About 500 people, some wearing masks and kerchiefs over their faces, marched through the city's downtown, breaking the windows of a Bank of America branch, a McDonald's outlet and a Starbucks shop, all symbols of the American capitalist system.
The crowd, which carried banners and at least one sign that read "Make Racists Afraid Again," largely dispersed after police responded in force.
About 900,000 people were expected to pack the grassy National Mall facing the Capitol, where Trump will be sworn in, as well as the parade route along Pennsylvania Avenue to the White House and other parts of central Washington.
Earlier, liberal activists with a separate group called Disrupt J20 intermittently blocked multiple security checkpoints leading to the largest public viewing area for the ceremony. Several were led away by police.
Disrupt J20 protest organizer Alli McCracken, 28, of Washington, said the group was voicing its displeasure over Trump's controversial comments about women, illegal immigrants and Muslims.
"We have a lot of people of diverse backgrounds who are against U.S. imperialism and we feel Trump will continue that legacy," McCracken said on a gray morning with light rain.
Trump supporters flooded into the capital, many sporting shirts and hats bearing his "Make America Great Again" campaign slogan.
Carl Beams, 36, from Howell, New Jersey, stood in line with thousands of Trump supporters waiting to enter the National Mall to view the midday (1700 GMT) inauguration.
"This is a great moment in history. I wanted to be able to say I was here firsthand," said Beams, who runs a martial-arts school.
He said he believed that Trump could be a unifying force: "I think he's sending the right message and doing his part to make that happen."
Banner / Thumbnail Credit : Reuters