More than a thousand May Day protesters decried racism, police brutality and income inequality on Friday in a plaza outside Oakland City Hall.
It was one of several demonstrations by labor, immigrant and civil rights activists in cities across California.
The protest in Oakland started with a loud, sign-waving march from the Port of Oakland to Frank Ogawa Plaza in downtown Oakland, where the crowd kept growing later in the day.
Some of the demonstrators held signs reading "Racism is the Disease," ''Black Lives Matter" and "Stop Police Brutality." Others said they wanted better wages and working conditions for the masses.
Maisha Davis, 29, a medical student at University of California, San Francisco is a member of White Coats for Black Lives.
"I'm here to support people for May Day," she told the San Jose Mercury News. "Police brutality impacts us all."
Across the bay, about 100 people gathered at Civic Center in San Francisco for a May Day rally before marching to the Mission neighborhood.
The annual May Day rallies have their roots in workers' rights, but events in recent years have been a rallying point for immigrant-rights groups and other causes.
This year, the use of force by police is a major focus following a series of incidents in which black men died in violent encounters with officers.
In Los Angeles, police kept watch as several hundred protesters gathered downtown to promote various causes, including a $15-an-hour minimum wage, immigrant rights and opposition to police violence.
Harberth Godinez, 25, of Los Angeles, a college student who was born in Guatemala, supported raising the minimum wage.
"There are a lot of families that earn the minimum wage and have two, three kids and they can't live with what they earn," he said. "That's not right."
Activists in Anaheim marched for legislation allowing millions of immigrants in the country illegally to apply for permanent legal residence.
And in Riverside County, advocates were planning a march through Murrieta, which drew national attention last year when demonstrators blocked buses carrying Central American immigrant families trying to reach a Border Patrol facility for processing.