Ron Dellums, a former mayor of Oakland, California and a former U. S. Representative from that state, passed away from cancer at his home on Sunday. He was 82.

The longtime politician was a left-leaning anti-war activist who was also pro-social justice, according to NBC Bay Area.

Dellums became the first African-American man from northern California to serve in Congress, according to the outlet, and represented the area’s 9th Congressional District from 1971-1998. He also served as the mayor of Oakland from 2007 to 2011.

Per NBC Bay Area, Dellums was involved in the U.S. sanctioning South Africa during that country’s period of apartheid; he spoke out against the U.S. entering wars; and he helped launch the Congressional Black Caucus.

“He spoke truth to power and appealed to America’s conscience in championing those who were left out and left behind, whether in the East Bay, across the nation, or around the world,” former President Bill Clinton tweeted on Sunday. “We will miss him.”

Rep. Barbara Lee (D-CA 13th), who replaced Dellums when he retired from Congress in 1998, expressed sorrow over the death of her “dear friend.”

“The contributions that Congressman Dellums made to our East Bay community, the nation, and the world are too innumerable to count,” she said in the statement.