Traditionally, the demonstrations are over economic inequality, workers' rights and social justice. But in Oakland, union workers, who made up a large part of the crowd of protesters at the Port of Oakland Friday morning, focused on a modern day issue: relations between police and people of color.
"The goal here is to affirm humanity for black people, brown people, oppressed people throughout America. We are here for no other reason," said Derrick Muhammad, a Local 10 business agent.
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One sign read: "Labor Power is the key! Stop the rule of the bourgeois!" Though organized by labor, hundreds of signs revealed a broad mix of community concerns.
VIDEO: San Francisco May Day March focused on Living Wage
"Working people care deeply about what happens to working people, and black people are part of the working class and as a whole, they're being mistreated," said Shonda Roberts, one of the marchers. "Police brutality is not good. We're losing our lives to the people who are supposed to protect and serve, taxpayer dollars."
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Police were on hand to escort the marchers, but there were no reports of any incidents.
With its large immigrant community, the South Bay has traditionally been vocal about the rights of workers and of pay issues.
Groups formed at several locations in East San Jose. The largest were at the corner of Story and King Roads, where elected officials were joined by labor leaders to rally.
The usual labor groups, immigration reform advocates, and elected officials turned out to give impassioned speeches.
Participants say there has never been more urgency for a May Day gathering as economic, labor and immigration issues converge. They think the rally and march send out an important message.
Nancy Contreras, a San Jose State senior, brought her four sisters and brother to the rally because of immigration reform and the escalating cost of living.
"This is one of the most expensive cities in the country to live in and yet we get paid $10 an hour. That's not enough to support whole families like all of these kids. There are so many kids in our family, and sometimes $10 an hour doesn't cut it," said Contreras.
It's an issue that labor leaders are focusing on.
"If we continue to have one-third of the households here unable to support themselves, that's a huge drain on the local economy," said Ben Field with the South Bay Labor Council.
Participants hope that there is growing awareness that the Bay Area economy is making it more difficult for low-wage earners to reach middle class status.
"The wages that are being paid do not make up for what it costs to live here. In Redwood City, the 2,000 apartments they built, a one bedroom is $2,800. Nobody's making that on $10 an hour," said Tom Linbarger, a local resident.
A new element to this May Day rally is inclusion of the message made popular by the hashtag "Black Lives Matter." It's a show of solidarity with events in Baltimore and in Ferguson.
Some reports indicate that this year's crowd is a bit smaller this year than in the past.
May Day originally started as a pagan ritual celebrating the start of summer. In the 19th century, labor movements starting using May Day as a day to recognize workers' rights.
The Port of Oakland has already scheduled its closure today, delaying operations for eight hours. Organizers are calling for protests to remain peaceful. Union leadership says, it's angry over social injustice -- specifically the police shooting death of Walter Scott, an unarmed black man who was killed during a traffic stop in South Carolina. Scott had family members who are Longshoremen.
May Day protests took place throughout the Bay Area, including San Francisco and San Jose. Nationally, big marches and rallies took place in Chicago, Philadelphia and New York.