Demonstrators smashed storefront windows and set rubbish and tyres alight in downtown Oakland, across the bay from San Francisco. A few miles away, students at the University of California at Berkeley protested on campus.
In Portland, Oregon, protesters blocked downtown traffic while chanting "not my president".
Hundreds of students in Pittsburgh, Pennsylvania, and Seattle, Washington, as well as in smaller towns around America, walked out of class in an effort to "stop president Trump".