The families of Michael Brown and Eric Garner were expected among the protesters in the heart of the US capital for the "Justice For All March" that was anticipated to be one of the biggest rallies of a movement sparked by the fatal August shooting of the unarmed Brown, 18, by a white policeman.
A grand jury decision last month not to indict police officer Darren Wilson over the killing in Ferguson, Missouri was followed by another grand jury decision that also declined to charge another white policeman in the "chokehold" death in Staten Island of father-of-six Garner.
Rice's family and relatives of Trayvon Martin -- shot and killed in Florida by a neighborhood watchman in 2012 -- were also expected to attend the march.
Ahead of the march several thousand people massed at Freedom Plaza, a short walk from the White House, shouting "No justice, no peace!" -- a signature chant of the nationwide demonstrations -- and listening to speeches.
"I am here not only for marching for Eric Garner, but for everyone's daughters and sons and nieces and nephews and dads and moms," Esaw Garner said.
Some in the crowd, which was made up of black and white people, many of them young, held aloft banners proclaiming, "Stop racist police," "I can't breathe," and "Black lives matter."
"I can't breathe" were the last words uttered by Garner, whom police wrestled to the ground in New York's Staten Island for allegedly selling untaxed cigarettes.
