Only one arrest was reported as about 200 demonstrators gathered Monday morning near a shipping terminal at the Port of Long Beach.
Police forced the demonstrators out of a parking lot but several dozen regrouped and briefly blocked a major roadway, backing up a line of trucks heading to the port.
Heavy rain dampened the protest and the demonstrators, who were flanked by dozens of police, have now moved off, effectively making a peaceful end to a four-hour protest.
Port spokesman John Pope says other routes are available and disruption has been minimal.
The demonstration was one of several aimed at ports up and down the West Coast.