What to know about May Day marches and rallies in Los Angeles

Thousands of people, including union members and immigrant-rights advocates, gathered in downtown Los Angeles and Boyle Heights Thursday for May Day rallies and marches.

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A group of union members and others will rallied near Olympic Boulevard and Figueroa Street in downtown Los Angeles to start a day of demonstrations. The group set out on a march east on Olympic Boulevard and north on Los Angeles Street, ending in the area of the Metropolitan Detention Center.

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Later Thursday, a May Day rally in Boyle Heights will begin at about 4:30 p.m. at Mariachi Plaza. A march is scheduled to begin about an hour later, also ending at the Metropolitan Detention Center on Alameda Street.

Another rally and march is planned at 4:30 p.m. at MacArthur Park, sponsored by the Community Self-Defense Coalition, which includes dozens of community organizations.

The marches come two days after thousands of striking Los Angeles County workers represented by SEIU Local 721 held a mass protest that moved through the streets of downtown. The SEIU strike began Monday night and ended Wednesday night.

Also in conjunction with May Day, thousands of University of California health care, research and technical workers will stage a one-day strike at UC facilities across the state. Their union, University Professional and Technical Workers, says the action is in response to a systemwide hiring freeze imposed by the UC in March, a move the union contends is exacerbating a staffing crisis in the system. The UPTE has been engaged in contract talks with the university, and the union staged a three-day statewide strike in February.

International Workers' Day is recognized in many countries around the world, with its origins dating back to the 1880s and initially supporting the establishment of an eight-hour work day. In the United States, the May 1 date was chosen to commemorate a general strike that began on the date in 1886 and ended with the Haymarket affair of May 4, 1886, when a peaceful rally in Chicago's Haymarket Square in support of workers ended with an unknown person throwing a dynamite bomb at police as they acted to disperse the meeting.

Eleven people were killed and nearly 200 others injured.