The bridge demonstration began around 4 p.m. when a group of cars spaced across the lanes began slowing down and stopping.
Protesters left their cars and began pulling a chain that linked all their cars on the span, according to the San Francisco Chronicle newspaper.
Traffic was completely halted and eventually backed up into the West Oakland interchange known as the MacArthur Maze, where Interstates 80, 580 and 880 merge just east of the bridge linking San Francisco and Oakland.
Officers from the California Highway Patrol officers began untangling demonstrators and reopening lanes beginning at 4:30 p.m., the newspaper said.
Twenty-five protesters were arrested, according to KCRA Channel 3 in Sacramento.
Mia Birdsong, a spokeswoman for the demonstrators, members of a Black Lives Matter movement offshoot named Black Seed, said the protest was designed to coordinate with Martin Luther King Jr. Day, the national holiday observed Monday.
“This action in particular was about taking a strong, courageous stand in solidarity with MLK,” she said.
Black Seed demonstrators were just one of several groups that protested all day in Oakland, Berkeley and Emeryville.
“We’re just trying to make the change we can and take it a day at a time,” protester Nkei Oruche, who marched on Shellmound Avenue in Emeryville with her husband and two children, told the newspaper.
Victor Guendulain of San Jose held up a sign that read “migrant workers for black resistance” as he joined the protest to “draw attention to the issues that black folks are going through and make the connection to migrant workers who face similar police repression and intimidation.”
Others in Emeryville held up signs calling for reparations, black resistance and black power, the newspaper said.
“I really respect how they’re making our rights known,” said spectator Olivia Duncan of nearby Hayward, Calif.
Most conversation at the protests centered on the tumultuous year since the last Martin Luther King Jr. Day in 2015
The past year saw riots break out in Baltimore after Freddie Gray, a young black man, suffered a fatal spine injury in police custody; the fatal shootings of nine black parishioners by a white man in a Charleston, S.C., church; and the declaration of a state of emergency in Ferguson, Mo., in the face of days of protests over the fatal shooting of Michael Brown by a police officer.
