Labor Day marches turned violent after 70,000 protesters clashed with police in the city's main square on Tuesday.
Authorities used tear gas and water cannons to disperse the tens of thousands and detained around 70 people.
One person was reportedly injured during the clashes.
Elsewhere May Day demonstrations were more peaceful, but no less passionate.
In the U.S., workers and rights activists joined forces to demand everything from fairer pay to immigration reform.
(SOUNDBITE) (English) DON LEE, MARCHER, SAYING:
"Los Angeles and the whole entire nation of the United States is built on the work of immigrants and every type of immigrant from German to Mexican-American."
Others worried over conditions for the growing number of impoverished Americans, struggling to put food on the table.
"People are sick and tired of their people sleeping on the streets in the cold, with rats and roaches in inhuman conditions. Police do nothing for you except to find reasons to lock you up. They make the streets only safe for the rich."
The rally, typically attended by union members, students and civil rights workers, was also joined by advocates from the Occupy Movement, gay rights coalitions and child trafficking groups.
Although they didn't share the same mission, protesters in Los Angeles marched together peacefully in support of various civil rights causes.
Labour Day is marked on May 1 by millions around the world.
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