Portland police said the person who was shot was taken to a hospital for treatment of injuries that were not life-threatening. Police said they were looking for the shooter, who apparently fled in his vehicle after the attack early today morning on a Willamette River bridge.
The shooting followed rowdy yesterday night protests, when police used tear gas in response to "burning projectiles" thrown at officers, police said on Twitter.
Hundreds of people marched through the city, disrupting traffic and spray-painting graffiti. Authorities reported instances of vandalism and assault during a rally that organisers had billed as peaceful earlier in the day.
In other parts of the country, spirited demonstrations on college campuses and peaceful marches along downtown streets have taken place since Wednesday. Hundreds joined a today afternoon "love rally" in Washington Square Park in Manhattan.
Leslie Holmes, 65, a website developer from Wilton, Connecticut, took an hour-long train ride to the demonstration - her first protest since the 1970s, when she hit the streets of San Francisco to oppose the Vietnam War.
She described herself as an armchair liberal but declared, "I'm not going to be armchair anymore." "I don't want to live in a country where my friends aren't included, and my friends are fearful, and my children are going to grow up in a world that's frightening, and my granddaughters can look forward to being excluded from jobs and politics and fulfilling their potential, so I'm here for them," she said.
Evening marches disrupted traffic in Miami and Atlanta. Trump supporter Nicolas Quirico was traveling from South Beach to Miami. His car was among hundreds stopped when protesters blocked Interstate 395.
"Trump will be our president. There is no way around that, and the sooner people grasp that, the better off we will be," he said.
"There is a difference between a peaceful protest and standing in a major highway backing up traffic for 5 miles. This is wrong."
More than a thousand protesters took to the streets across California after night fell including downtown Los Angeles, where over 200 were arrested a night earlier.
In Bakersfield, where Trump is far more popular than in most of the state, some held signs reading "Anti-Trump, Pro-USA."