In downtown Los Angeles, several thousands of demonstrators marched north on Broadway from Olympic Boulevard. A key issue was immigration reform for the estimated 11 million undocumented immigrants living in the U.S.
"There's no reason we should have second-class individuals in this country. I mean, this is the United States. We come here for a reason," said Jorge Garavito, a member of the Coalition for Humane Immigrant Rights of Los Angeles.
Calls for immigration reform are nothing new at May Day marches in Los Angeles. But adding urgency to this year's event was a bipartisan group of senators' wide-ranging, 844-page immigration reform bill.
Demonstrators were out at 4 a.m. getting their message out with signs in hand.
Anton Farmby, a member of the Service Employees International Union, said it all boils down to equal rights for all.
"As a union member, it's time that we create a pathway to citizenship for the undocumented workers in this country," Farmby said.
Other demonstrators who joined the masses were calling for an end to the Federal Reserve.
The crowd marched to the Placita Olvera, where rallies and performances continued.
Several downtown roads were slated to be closed until 8 p.m.
Tens of thousands of marchers took part in last year's event. In light of the tragedy in Boston, organizers requested extra security for marchers this year.
Organizers also asked protestors to be cooperative in order to prevent violent clashes like in 2007.
Other demonstrations were also held around Southern California.
There was a strong show of support for immigration and workers' rights in San Bernardino. Hundreds of people were on hand for the rally organized by local labor groups.
In Orange County, a counter-protest was held by members of the group We the People California's Crusaders. They gathered on a bridge overlooking the 91 Freeway in Anaheim, saying the nation's focus should be on the unemployed and the poor. One sign read, "No Amnesty."
"Homelessness is burgeoning, our American veterans live in poverty, and that should be the focus of our elected officials, not individuals who are living in this country illegally," said protester Robin Hvidston.
Students from Long Beach City College protested against deep cuts in vocational education. They say 40 percent of the student population is affected and they want to save the trades program.
Around the world, laborers in Indonesia, Cambodia and the Philippines marched and protested against being squeezed by big business.
In Istanbul, Turkey, things got out of hand when demonstrators clashed with police after the mob tried to break through a barricade. Officers used water cannons to push the crowd back. Protesters retaliated by throwing stones.