Ron Dellums, the son of a longshoreman who became one of America’s best-known black congressmen, a California Democrat with a left-wing agenda that put civil rights and programs for people ahead of weapons systems and warfare, died early Monday at his home in Washington. He was 82.

His death was confirmed by Dan Lindheim, who was an aide to Mr. Dellums on Capitol Hill and was city manager of Oakland when Mr. Dellums was a one-term mayor there a decade ago. Mr. Dellums had cancer, he said.

A former social worker representing Oakland and Berkeley, perhaps the nation’s most liberal congressional district, Mr. Dellums went to Washington in 1971 as a fiercely liberal — some said radical — firebrand protesting the Vietnam War.

He demanded a House investigation into American war crimes in Vietnam. When his pleas were ignored, he held his own informal hearings, which drew national attention. As antiwar protests raged outside the Capitol, a former Army sergeant told in unsworn testimony how he and his platoon had massacred 30 men, women and children in a Vietnamese village. It was a shocking beginning.