Seattle police arrested 19 people after marchers blocked a portion of Highway 99, triggering heavy delays on Monday afternoon.
Police said the protesters, chanting "black lives matter," blocked the roadway around 2:30 p.m., then blocked traffic at the Mercer Street/Interstate 5 exit.
Police cleared protesters from the roadways, and by about 4:30 p.m. both State Route 99 and the interstate off ramps were opened to traffic.
One officer was injured during the incident, police said. The officer was taken to Harborview Medical Center, where he was treated and released.
Organizers said they were engaging in "civil disobedience" to protest police violence.
