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00:02Mount Rushmore, four colossal heads of some of America's greatest presidents immortalized in
00:08granite. It's beyond ambitious. It is monumental. It's one of the most recognizable images on the
00:16planet. But today, investigators uncover new secrets hidden inside this modern-day engineering
00:22wonder. It's kind of working on a puzzle with half the pieces missing. New evidence shows
00:28how the epic challenge of shaping a whole mountain nearly defeats its creators.
00:35You can't just blow everything up and take all the rock off. And what could destroy it?
00:41There are 140 fractures in there all over the sculptures, above it, below it, behind it.
00:47What are the secrets of its construction? And why is America's most famous landmark created
00:52on a mountain in remote South Dakota? To find out, we will blow apart Mount Rushmore and rebuild
01:01it to its astonishing original design. We'll explore its buried tunnels and hidden chambers
01:10and reveal the high-tech secrets concealed within this mysterious mountaintop megastructure.
01:22South Dakota, 5,000 feet up a mountainside. The giant granite faces of George Washington,
01:34Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln stare out sternly over the beauty of the Black Hills.
01:47Mount Rushmore.
01:48Mount Rushmore. But behind these familiar likenesses lie clues to what this monument is really for.
01:57Why these four men are here. And evidence of how you carve a granite mountain on a scale no one
02:03thought possible.
02:05It's a monumental project, because it hadn't been done before.
02:13Painstakingly carved into the Black Hills, four faces, each towering 60 feet tall.
02:23Hollowed-out irises plunged two feet into the cliff, leaving a thin pillar to appear like a sparkle in their
02:30eyes.
02:33And finally crafted facial hair, each taller than three people, carefully perched spectacles, 12 inches thick, and finely crafted facial
02:45hair.
02:47These incredible sculptures total 14 years in the making.
02:52How do you build such an epic monument?
02:57It's the brainchild of Danish-American sculptor, Gutsen Borglum.
03:02Historian Laura Pankritz investigates how Borglum carves his giant masterpiece from a solid mountain.
03:10Gutsen. She wants to know how he deals with the epic engineering challenge he faces at Mount Rushmore.
03:16Gutsen was a very ambitious person.
03:18He would say things like, there was great civilizations in Rome, incredible monuments in Egypt.
03:26I want this monument to be around for thousands of years.
03:31Mount Rushmore's creator attempts a feat of precision engineering not seen on this scale in the United States before.
03:37It was very different to be able to remove a small piece of stone in the studio in comparison to
03:46removing 450,000 tons of rock off of the mountain.
03:50And one mistake, and there's no putting it back.
03:57Gutsen Borglum's first challenge?
03:59To find over 400 workers used to working with rock-hard granite.
04:04The Depression was going on, so there wasn't a lot of work.
04:08There was a lot of unemployed miners here, and they were happy to go to work for Borglum.
04:15Mines are dotted right across South Dakota.
04:19Miners here have years of experience removing thousands of tons of hard rock in search of valuable minerals,
04:25such as mica, natural stone, and gold.
04:30Borglum harnesses their pioneering mining technology to start transforming a remote mountain of granite
04:36into a magnificent monument.
04:41In 1927, they begin carving.
04:44But instead of using chisels, workers use dynamite.
04:52They blast away the mountain to create four giant heads of smooth rock.
04:59Next, they drill three-inch holes all over the rock's surface to carve the features of the famous faces into
05:07the rock.
05:08And for the finishing touches, they use air-powered hammers to smooth the sculpture.
05:15But how can you accurately carve a mountain with dynamite while dangling over 50 stories high?
05:29Wayne Van Hoot runs the Millbank Granite Quarry in South Dakota.
05:34He's an explosives expert and granite cutter.
05:38Granite is extremely hard to work with.
05:40A shortcut in that is we can use explosives.
05:43But when you use explosives, if not done right, it can cause damage to the stone.
05:49Wayne wants to understand how the workers at Mount Rushmore use dynamite so accurately.
05:55He experiments with their techniques.
05:58He starts by testing explosives on a reject granite block.
06:02We'll put one stick of dynish here in each hole.
06:06The holes here are drilled random.
06:17Oh, that's how you break it up good.
06:20Of course, you don't end up with much left when you're done.
06:24How do you carve a face using explosives without causing this much damage to the monument?
06:31Here, if we make a mistake on blasting, we wrecked a good block, and it's a financial burden on Mount
06:39Rushmore.
06:40There, they wrecked a mountain, and you can't replace that.
06:45Wayne needs to blast off the excess wedges of granite from around the base of these large blocks.
06:51He needs to carefully calculate how to direct the explosion, just as the workers do on Mount Rushmore.
06:59First, he cuts a series of holes along the line where he wants the rock to break.
07:04They'll each hold a small explosive charge.
07:07We've already weakened this surface by drilling the holes.
07:10When we shoot it, the blast is going to follow that line.
07:14Now it will break right on that line, and we don't have to worry about damaging the stone ahead of
07:19it or behind it.
07:21If Wayne has calculated correctly, then only the uneven granite should be blasted off.
07:27Leaving three perfect blocks.
07:30Here he goes.
07:41Looks great.
07:43The line of drill holes precisely directs the explosive force.
07:49It removes only unwanted granite, and leaves the remaining rock unspoiled.
07:55Out here, we can do a blast pretty much any time of the day.
08:01That Mount Rushmore, they used to do it twice a day.
08:05The reason for that was they had to clear the mountain when they did do their blasting.
08:10Everybody had to find what the ropes get off the mountain.
08:12It must have been quite an ordeal to get it done.
08:16In the hands of experts, the dynamite technique can remove rock to a remarkable accuracy of within three inches.
08:25At Mount Rushmore, this leaves behind a rough outline of the face.
08:30But how do you sculpt the final few crucial inches?
08:33On Mount Rushmore, they would have come in with jackhammers, start grinding that away, make it smooth.
08:39The polished face, they call it.
08:41The workers remove the final three inches with a technique called honeycombing.
08:46They use jackhammers to drill a tight pattern of holes.
08:50This weakens the granite and allows small pieces to be accurately removed with hand tools.
08:56They pound the rock to a smooth finish by loosening the drill bit in their air hammers, a method known
09:02as bumping.
09:05I've got a small 12 by 12 area done.
09:07Went really fast for me, but I'm not hanging from the rope off the side of a mountain trying to
09:12go straight in with this.
09:14Trying to make it all the perfect shape.
09:17But when you're all done, this is what they call their polished surface.
09:20It looks great.
09:21Achieving this level of detail at the giant scale of Mount Rushmore will take 14 years.
09:27It's an incredibly complex operation.
09:34When Borglum arrives in the Black Hills wilderness, there isn't even a road here.
09:39To realize his epic vision, he needs giant infrastructure.
09:44A small city springs up at the bottom of the mountain.
09:48Complete with new roads, blacksmith shops, and tool sheds.
09:56A steep 760-step staircase and a cable car.
10:01Take the workers to the top of the mountain over 5,000 feet high.
10:07Winches lower the carvers down onto the faces, dangling hundreds of feet above the ground.
10:18Giant compressors pump air up the mountain.
10:21To power the pneumatic drills and custom-made air hammers.
10:28Mount Rushmore is the first project of its kind in the United States.
10:33So the mountain carvers must adapt or invent all the tools and techniques they need from scratch.
10:39It was a learning experience for them.
10:42An experiment in how do I hold these tools?
10:45How do I keep them in place as I'm suspended over the side of the mountain?
10:50Workers move around the cliff face in a special harness called a bosun seat.
10:55It's used on sailing ships, so sailors can safely reach the rigging.
11:00Gutsun Borland adapted and adjusted the bosun seat for use on the mountain.
11:05He had to invent tools.
11:07He had to make tools better.
11:09He was ingenious in all of those areas.
11:13Hundreds of specialists are recruited and trained, from powder men and blacksmiths to winchmen and callboys.
11:21It was very noisy where the winches were running, and they couldn't see the men over the side of the
11:27mountain.
11:28So Gutsun had a collar on the top who would see where the men had to go
11:33and let the winches know what they needed to do when they needed to do it.
11:39Amazingly, in the 14 years, they had zero casualties.
11:45But the mega-project creates constant challenges that force Gutsun Borland to change his plans.
11:52Today, investigators unearth the unexpected problems he finds hidden within the mountain itself.
11:59How does its natural geology affect the design of the Icon we know today?
12:18Mount Rushmore, South Dakota
12:25Today, it's a famous Icon.
12:29But this isn't how its creator designs it.
12:32Now, researchers are examining why Gutsun Borland radically transforms his original vision.
12:38It's kind of working on a puzzle with half the pieces missing.
12:43He starts out trying to make something that looks very different.
12:47He plans four busts.
12:50With Jefferson on Washington's right.
12:53And Lincoln nestled behind his left shoulder.
12:58All carved right down to their waists.
13:03This layout leaves space for a giant tablet.
13:07120 feet high.
13:09In the shape of the Louisiana Purchase.
13:13It documents key dates in American history in three-foot-tall gilded writing.
13:18So why is Mount Rushmore today so different from the original plan?
13:26Mark Ferenbach is a geologist for the state of South Dakota.
13:31As we can see, most of it is the whitish-colored, harney-peat granite.
13:38Mark investigates and maps the complex geology of this area by studying the surface rock.
13:45He wants to know how Mount Rushmore's internal structure forces its creator to change his design.
13:51As you get in, there could be little pockets and seams and veins where you have different rock types.
13:58Gutsun Borland was looking for rock that had fairly fine grain.
14:02And the grain size in the harney-peat granite ranges quite a bit.
14:07From just small little grains, maybe a centimeter, to large crystals five, ten feet across.
14:16Borglum needs rock made up of smaller mineral crystals because they have a stronger structure.
14:22It lasts far longer and will give his faces a realistic look.
14:26The crystal size is determined deep in the Earth's history.
14:331.7 billion years ago, the Black Hills area is made up of layers of soft, sedimentary rock,
14:39with molten magma forming deep within the Earth.
14:44The magma pushes up between the layers of soft rock and cools quickly, solidifying into smooth, hard granite.
14:55Over time, cracks in the granite fill with more magma, cooling slowly, leaving behind crystalline streaks in the smooth rock.
15:06The surrounding softer rock wears away, exposing the streaked slab of granite that Borglum begins to carve.
15:17How does the Earth's geological past force Borglum to change the final design of Mount Rushmore?
15:24Mark investigates these early templates for the monument.
15:27He compares them with photos of the construction in progress.
15:31He wants to see if he can find clues in the rock structure that explain why Rushmore today looks completely
15:37different from these original models.
15:41Four years into the work, they have an almost complete George Washington, but then they move on to Thomas Jefferson.
15:49This photo shows where they were preparing to put Thomas Jefferson, and on the model over here, Thomas Jefferson is
15:56to the right of George Washington.
15:59You can see part of the eye developing and the nose developing.
16:04But after two years of back-breaking work, they hit a problem.
16:09It looks like as he was carving that, he got into some bad rock there that was too coarse grain
16:16or just unstable.
16:18The slower-cooled large crystals he finds in the granite here are difficult to carve accurately.
16:23If they continue and the rock doesn't improve further into the mountain, they won't be able to complete Jefferson's face.
16:30It's very frustrating for Gutz and Borglum.
16:33He'd prepare an area, you're digging in there, but your rock's not getting any better.
16:39If the rock won't support the sculpture, no matter how much he wants to put it there, it's not going
16:45to happen.
16:46Borglum orders two years' work on Jefferson to be dynamited off the mountain.
16:55He goes back to the studio to rethink.
17:00He eventually decides to move Jefferson's head to a new position.
17:04But when he starts work, Borglum discovers another potentially catastrophic surprise in Mount Rushmore's hidden geology.
17:11It looks like there's a coarser grain running right through his nose.
17:16Larger crystals in the coarse grain will weather away more quickly and leave a scar down his nose, wrecking the
17:22whole monument.
17:24The differences with the mountain today reveal the ingenious solution.
17:29If you compare to the earlier model, the expression on the mouth has changed a little bit.
17:34The eyes have changed a little bit.
17:40Gutz and Borglum changes the orientation of Thomas Jefferson's face from looking almost straight out to looking a little bit
17:49to the left.
17:50And by doing this, he was able to shift the position of that coarser grain granite diek to kind of
17:56going down behind the nose and onto the face.
18:02Each tiny change of plan takes months of work to complete.
18:08Finally, the order of the presidents is settled.
18:10But there's no room for the giant tablet of the Louisiana Purchase.
18:15Now he needs to tackle the president's elaborate clothing and upper bodies as on the final model.
18:20In a photo of Mount Rushmore from before the carving begins, Mark finds evidence of more problems.
18:28Right in the place where they put George Washington, you can see a dark band, and that is mica schist.
18:35Micah schist is a much weaker rock than granite.
18:38It can easily split during carving and weaken the monument.
18:42George Washington does have lapels, but as you go halfway down to the chest, that's where he had to stop.
18:49He couldn't carve into the mica schist because that weathers very easily, and it's not strong.
18:56Most of this mica schist is now hidden by the thousands of tons of debris removed from the mountain above.
19:03The president's completed faces on Mount Rushmore do look almost identical to this final clay template.
19:13How do stonemasons transfer the precise contours of the ever-changing models without modern-day laser scanners?
19:21Clues lie in another mysterious mountain carving emerging from the Black Hills granite today.
19:40Mount Rushmore, a giant granite monument of four iconic U.S. presidents.
19:46To build it, its creator first makes a finely crafted clay model.
19:51But how do the workers translate this artwork into a colossal piece of engineering?
20:00Nine miles southwest of Mount Rushmore, another giant monument is slowly emerging from the mountainside, built using the exact same
20:09methods.
20:13The face of the Native American warrior Crazy Horse towers 30 feet taller than the faces on Rushmore.
20:22It's been in the making for 70 years, but it's far from complete.
20:28His flowing locks will take another 10 years, and his body will be carved from over 10 million tons of
20:35granite, revealing the warrior pointing his 227-foot-long arm as he rides his horse.
20:43When finished, it will be the biggest sculpture in the world.
20:47But how do you scale up a model into a sculpture the size of a mountain?
20:57In 1948, one of the original carvers of Mount Rushmore, Korchok Joukowsky, starts the Crazy Horse Project using the techniques
21:05he learns there.
21:07Dad was assistant sculptor for a year to Gutsen, and if it weren't for Mount Rushmore being carved, Dad never
21:14would have been able to start this mountain carving.
21:16Now, his daughter, Monique Joukowsky, continues her father's colossal creation.
21:23In 1948, the first blast on the mountain was set off, and we've been here for 70 years.
21:32Mountain carver Monique still works from her father's scale models.
21:36Just like Rushmore's creators, she uses a pointing machine, an ingenious ancient Greek device to map the scale model onto
21:44the mountain.
21:45This is our 134th scale model.
21:47So one inch here equals 34 inches up on the Crazy Horse's head.
21:53The first step is to get an accurate measurement of each point on the model from a fixed spot the
21:58machine pivots around.
21:59So X, Y, Z coordinates, and there's been 10,000 of those taken on Crazy Horse's face.
22:05It's a labor of love.
22:07The carving team high up on the mountain translates the measurement of the model onto the rock's surface.
22:13To do this, they use scaled-up versions of the pointing machine.
22:16Right now, we're going to do the outline of the fingernail.
22:20Once we establish where this pivot point is for carving this area on the mountain, we won't move it.
22:26So it stays accurate because it stays put.
22:29First, they match the measured angle from the pivot point.
22:32Where Jesse is now, when he turns the pointing machine out to go alongside Crazy Horse's finger, those are east
22:40and west degrees.
22:41Then they move the plumb bob horizontally along the crane arm before dropping it down to the rock.
22:47They compare the distance it falls with the model measurement.
22:51Those measurements tell us how much rock we have to move to get down to finish drain.
22:57Any mistakes in the calculation could ruin 70 years of work, so they need to be certain before they begin
23:04removing rock.
23:06When you're pointing, you measure way more than one time to get to finish grade, so there's a lot of
23:12checks.
23:13Crazy Horse's image emerges inch by inch from the mountain.
23:17But why is this Native American hero being carved here?
23:25The Black Hills belong to the Native American Lakota people, which the U.S. government recognizes in 1868 in an
23:33official treaty.
23:36But in 1874, the gold rush takes over the Black Hills and forces the Native Americans off their land.
23:47Crazy Horse, a Lakota chief, goes to war to win back the sacred hills.
23:52But despite his bravery, the lands are lost.
23:57In 1931, demands to put Crazy Horse onto Mount Rushmore are rebuffed.
24:02So Native Americans plan their own monument in his honor.
24:09The carving of Mount Rushmore, I'm sure, hurt the Native American people.
24:14And if they're going to carve a mountain to quite a few white people, then perhaps they should carve a
24:20mountain in the Black Hills to a Native person.
24:24The Crazy Horse carvers use public donations to complete a monument that will eventually be over ten times the size
24:30of the carving on Mount Rushmore.
24:34Dad felt if the interested public wanted to help carve this mountain, that they would.
24:39And they have all these years.
24:44It's painstaking work.
24:46The rock was eight feet above Crazy Horse's finger and came straight across.
24:51And all of this rock has been moved in the last five years.
24:55To improve speed and accuracy, Monique now adds modern methods to the traditional techniques pioneered on Mount Rushmore.
25:03They adapt the latest diamond-tipped cable saws from the quarrying industry.
25:08There's not as much vibration on the rock as you drill and drill and drill.
25:13And it's very accurate.
25:14And you can make some pretty nice shapes and fit it in places where you maybe couldn't reach with your
25:19drills.
25:21They complete the final finish with an extremely high-temperature torch that flakes the final few millimeters of rock away.
25:30This is what the rock looks like after it's been torched.
25:33It's that same finish as Crazy Horse's face.
25:35And this is the tip of Crazy Horse's finger.
25:39That is this right here.
25:44Crazy Horse could eventually take two centuries to complete.
25:49Compared to Mount Rushmore's 14 years.
25:53You can't just blow everything up and take all the rock off.
25:57There's a lot more that goes to carbon and mountain than that.
25:59So as long as we keep making good, steady, and safe progress, then that's what matters.
26:06Crazy Horse and Mount Rushmore are vast monuments.
26:11Designed to amaze for generations to come.
26:14But inside Mount Rushmore are secret chambers and buried caskets.
26:19What can they reveal about this iconic monument's message to people far in the future?
26:38Mount Rushmore is one of the most recognizable images on the planet.
26:44But is it simply a colossal structure, or does it have another purpose?
26:49Clues are hidden inside the mountain.
26:55Behind Abraham Lincoln's head lies a secret tunnel extending 70 feet deep into the rock till it hits a dead
27:06end.
27:08But at the tunnel's mouth, a 1,200-pound granite capstone seals an underground chamber.
27:14Inside, a titanium vault that contains a long teak casket.
27:23And carefully stacked inside, 16 super-thin enamel panels.
27:29Why are these mysterious tablets hidden inside Mount Rushmore?
27:33And why is there a tunnel that seems to lead nowhere?
27:39In Washington's Library of Congress, architectural historian Paula Reed hunts for an explanation.
27:47There are thousands of documents detailing Mount Rushmore's evolution among the personal papers of its creator,
27:54Gutzon Borglum.
27:55There's a lot of correspondence dealing with Congress to get funding.
27:58A lot of the funds were matched with private funds,
28:01so there was also going out and beating the bushes for private donors.
28:06So funding was a problem from the beginning.
28:10The monument is initially budgeted at $250,000.
28:15But costs rocket to nearly $1 million.
28:19They kept running out of money, and there would be an appropriation, and it would get spent.
28:23And then work would stop.
28:25And then there would be another appropriation.
28:28And here we have records that were kept in 1939 and 1940.
28:33Paula works with the collection's historian, Barbara Baer,
28:37to investigate why the project keeps running out of money.
28:41Gutzon Borglum did change his mind a good bit, and things evolved.
28:47Gutzon Borglum's vision of Mount Rushmore keeps expanding.
28:51They're searching out evidence for his most audacious and expensive plan.
28:56So these are oversized items.
28:59Original blueprints reveal detailed designs for a complex around the finished monument.
29:05Part of the proposal of Gutzon Borglum was to have this grand staircase
29:10that would allow visitors to climb all the way up behind the heads.
29:16The staircase leads to the majestically titled Hall of Records.
29:21Gutzon Borglum describes a chamber hidden within the mountain
29:24that explains Mount Rushmore's purpose
29:26and houses a depository of the country's most sacred texts.
29:30It would have copies of important documents like the Declaration of Independence,
29:35the Constitution, and an explanation of who the heads were
29:40and why they were on that mountain.
29:42But could the chamber hold more than just an explanation of the mountain carving?
29:47Gutzon Borglum reveals his master plan for the Hall of Records
29:51in his unpublished personal memoir.
29:54It's an interesting thing that it's another argument about the larger plan.
29:58And that's Borglum's handwriting, where he was editing himself.
30:05Gutzon Borglum plans a grand hall, 80 by 100 feet, drilled behind the faces,
30:11with an 800-foot-high granite stairway climbing up to it.
30:16At the chamber's grand entrance, a bronze eagle, with wings spanning 38 feet,
30:22sits above huge glass doors.
30:27Inside, bronze and glass cabinets line the walls,
30:31showcasing historical documents like the Declaration of Independence.
30:39Busts of famous Americans decorate the hall,
30:42and the nation's contributions to the world are inscribed on the walls.
30:50Gutzon Borglum wants to secure Mount Rushmore's place
30:53among history's greatest monuments,
30:55and idolize America's achievements for any future civilization discovering it.
31:01Gutzon Borglum was so attracted to these kind of ideas of colossal shrines,
31:07like the pyramids.
31:09You see from the outside this very monumental structure.
31:13But if you go in the inside, there's this secret chamber
31:16that tells us the story of that time period.
31:21The records show that he persuades Congress to grant $50,000
31:25for the construction of the Hall of Records.
31:29In 1938, workers start blasting the cavity for the hall out of the mountain.
31:36But the approach of World War II forces a halt.
31:41Congress said, we need this money for the war effort,
31:44so we're done here.
31:46Don't worry about the Hall of Records.
31:48Don't worry about the Grand Staircase.
31:50Just get the heads done.
31:52The heads are swiftly completed,
31:54and work on the monument stops in October 1941.
31:58The Hall of Records, which had been started,
32:00is still left there in its unfinished state.
32:04The half-completed Hall of Records
32:07still shows the tool marks of the halted construction.
32:10But in 1998, Gutzon Borglum's daughter
32:14buries the 16 enamel tablets in the entrance to the chamber.
32:18This time capsule contains a history of the United States
32:22and biographies of the four presidents and Gutzon Borglum.
32:26They also detail the epic struggle to get the giant monument built.
32:31But why is this national memorial started in the first place?
32:35And what can investigators discover about why it's here, in remote South Dakota?
32:55South Dakota's Mount Rushmore.
32:58It's an American icon.
33:00But why is it built in the first place?
33:03And why is it here, in South Dakota's Black Hills?
33:08Architectural historian Paula Reid pieces together archives from across the country.
33:14She wants to find out where the idea for this unprecedented monument comes from.
33:19People are surprised because, you know,
33:21they just think that Rushmore was always planned as is.
33:28Letters between the project's early backers reveal the first concept for the mountain carving
33:33has nothing to do with presidents or democracy.
33:36His original idea was to do more regional and local figures rather than these national heroes.
33:44And also to do them on a much, much smaller scale.
33:47In the 1920s, South Dakota state historian Doan Robinson looks for a way to boost the economy in his remote
33:55state.
33:56Doan Robinson wanted to carve figures of the Old West in the Black Hills area that would become a tourist
34:05draw.
34:05It was a much, much smaller scale operation.
34:10The faces of Old West heroes, like Buffalo Bill and Sitting Bull, could today be staring out of the Black
34:17Hills.
34:18How does this idea get transformed into a massive mega project with the president as its heroes?
34:25Doan Robinson's letters recount the first time Mount Rushmore's creator arrives in South Dakota.
34:31Doan Robinson selected Gutz and Borglum and it was an experiment at first.
34:35He invited him to come and visit to see what he would do and also to prepare a proposal and
34:41a price quote.
34:42Robinson first brings Gutz and Borglum to this famous rock formation called the Needles.
34:48But Borglum rejects the thin spires and fractured granite as unsuitable for portraits.
34:54He spends weeks trekking across South Dakota's stunning, rugged landscape looking for a suitable site.
35:02Letters between the South Dakota promoters reveal that Gutz and Borglum is inspired when he finds the perfect location.
35:10When Borglum saw Mount Rushmore in its natural state, he said, this is where I want to do something major.
35:18He proposes a gigantic carving, an unprecedented colossus of national significance.
35:25In reading the correspondence, I'm surprised that they went along as quickly as they did.
35:31I don't think they really envisioned that it would be possible to do something on the scale of what Mount
35:38Rushmore became.
35:39And no one had ever done it before.
35:43By 1925, when Borglum is planning Mount Rushmore, 28 presidents have held office.
35:49Why does he choose these apparently unconnected four?
35:53Paula finds clues in Gutz and Borglum's prolific writing.
35:57I think they were unified in Gutz and Borglum's mind.
36:00He referred to them as empire makers or empire builders.
36:06George Washington is the country's founding president.
36:09It's pretty much an automatic thing to put him on the mountain as the most prominent of the four heads.
36:15And in addition, during his term, the United States expanded in its territory toward the west.
36:21Third president, Thomas Jefferson, is also a founding father.
36:25Well, he drafted the Declaration of Independence.
36:28Then, as president, he greatly expanded the territory in the United States with the Louisiana Purchase.
36:35Abraham Lincoln preserves the Union of the United States by winning the Civil War.
36:41Theodore Teddy Roosevelt is the last and perhaps most surprising choice.
36:46First of all, he was a friend of Gutz and Borglum's.
36:49But he also was, as Borglum would say, an empire maker.
36:52The United States completes the Panama Canal and it becomes U.S. territory under Roosevelt, securing America's prosperity.
36:59All four of the people who are on Mount Rushmore would become a symbol of America emerging from its beginnings
37:08into a major power.
37:11Gutz and Borglum creates these four icons of the American presidency out of the epic landscape of the nation they
37:17build.
37:17By daring to work at this unprecedented scale, his vision becomes a temple to the United States' founding ideals.
37:26But how long can this symbol of American achievement last?
37:30What threatens this iconic memorial?
37:46Mount Rushmore, a shrine to four of America's greatest presidents, designed to inspire today's citizens and impress future civilizations.
37:57But how long can this iconic monument last?
38:00There are 140 fractures, and they're all over the sculptures, you know, above it, below it, behind it.
38:10The granite faces are exceptionally tough.
38:13But tiny fissures in the rock can allow rainwater to trickle in.
38:21As it freezes, it wedges open the cracks.
38:27With potentially catastrophic results.
38:34To prevent this, the team at Rushmore fills any cracks with a waterproof sealant.
38:41And to detect even the tiniest movement, they install a network of highly sensitive motion sensors.
38:48Will this be enough to protect Mount Rushmore for centuries to come?
38:53We can measure down to a thousandths of an inch resolution.
38:58Engineer Cody Vining is an expert in rock mechanics.
39:02He's tasked with monitoring any deterioration in Mount Rushmore.
39:06The biggest concern is where fractures intersect inside the rock.
39:11When they intersect, they form a discrete block, and that have the potential to move from their current location.
39:20Cody and his team monitor the network of high-tech movement sensors around the faces.
39:25They capture any microscopic change in the width of the fractures surrounding these blocks.
39:30Here is our real-time feed from the instruments up at Mount Rushmore.
39:35We are measuring seven-thousandths of an inch displacement.
39:40Right now, an exposed block in the side of George Washington's cheek causes the most concern.
39:45We got the exposed rock up there.
39:47It snows.
39:48Snow accumulates.
39:49Sun comes out.
39:50It melts the snow, and it can percolate down into these fractures, and the water can freeze.
39:55The expansion of the ice can exert quite a bit of force on the rock.
39:58This process is called the freeze-thaw cycle.
40:05In cold weather, water in the cracks can freeze, pushing the cracks open.
40:11Then, as the weather warms up, the ice melts.
40:15If this cycle keeps repeating, the cracks grow larger and larger, and whole blocks can become wedged apart.
40:25The original carvers, they knew that these fractures had the potential for water to percolate in them.
40:30To reduce that freeze-thaw cycle, you know, they patched the top with linseed oil and granite dust.
40:36Cody checks that the sealant is still working.
40:39He uses sensors so accurate that he can see Mount Rushmore reacting to the weather.
40:43When the rock changes temperature, it changes shape.
40:48We see variation hour to hour, and then we can really see the fluctuation and the displacements through the seasons.
40:56The instruments also measure minute temperature fluctuations.
41:00So Cody can take into account these natural rock movements in his calculations,
41:05and work out if the blocks are slipping further than expected and damaging the sealant.
41:13He determines that Mount Rushmore is stable for now.
41:17But this state-of-the-art system will sound an early warning of any critical deterioration.
41:22As long as we keep monitoring it, and they maintain the seal to prevent water from filtrating into the fractures,
41:28there's no reason this sculpture won't be there for tens, thousands, hundreds of thousands of years to come.
41:37Mount Rushmore, a monument shaped by the geology of South Dakota,
41:43and transformed by a feat of ingenious engineering,
41:48with hidden messages of American greatness for future civilizations,
41:53an icon to inspire all Americans.
42:10Mount Rushmore, an icon to inspire all Americans.
42:27Mount Rushmore, an icon to inspire all Americans to bizarre and covertly travel into the deserts long mountains.
42:29Mount Rushmore, a monument camp forjährate all Americans.
42:29Mount Rushmore, a monument at the Alanде Park.
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