Protesters gathered at Emerson Park in downtown San Luis Obispo on Wednesday for a demonstration in support of Black Lives Matter.
The gathering began at about 5:30 p.m.
A social media post about the protest encouraged participants to bring water, wear a mask, and make signs.
Demonstrators also planned to march through downtown streets with a police escort.
Approximately 200-300 people joined the march Wednesday evening.
Protesters were calling for charges to be dropped against Tianna Arata.
The 20-year-old was arrested following a protest in July, during which protesters blocked Highway 101. San Luis Obispo police said Arata was responsible for leading the march and claimed several acts of vandalism had occurred at the hands of protesters.
The California Highway Patrol and Caltrans shut down several on and off-ramps along Highway 101 through downtown San Luis Obispo as a precaution during Wednesday's protest.