Edward Brooke, the first African-American senator to be popularly elected in the US, has died aged 95.
Brooke died of natural causes on Saturday at his home in Coral Gables, Florida surrounded by family, his former aide Ralph Neas said.
The liberal Republican was elected to Congress by Massachusetts voters in 1966 at a time of intense racial turmoil during the civil rights movement.
A former lawyer, Brooke had also been the first African-American to hold the post of attorney-general in any state when he was elected senator.
He served in the Senate until 1979 and played an important role in passing the Fair Housing Act of 1968, which prohibited racial and religious discrimination by housing providers.
Brooke campaigned in favour of the Equal Rights Amendment and defended school busing (providing transport to allow children living in areas predominantly populated by ethnic minorities to schools in primarily white neighbourhoods) as part of nationwide attempts to achieve racial integration.
The former statesman opposed Republican President Richard Nixon and was the first Republican senator to publicly call for the leader's resignation after the Watergate scandal.
Brooke was re-elected by a huge margin in 1972, but lost a bid for a third term in office in 1978, after which he returned to private practice.
Brooke's exit from national politics is believed to have been sparked by an acrimonious public divorce from his wife of 31 years, Remigia, late in his second term. Repercussions from the case led to an investigation into Brooke's personal finances by the Senate Ethics Committee and a probe by the state welfare department, which ultimately cost him the 1978 election.
In a 2000 Boston Globe interview, Brooke said: "It was just a divorce case. It was never about my work in the Senate. There was never a charge that I committed a crime, or even nearly committed a crime.
"I would certainly not be truthful if I didn't say I was sorely hurt when the people of Massachusetts voted against me and didn't look beyond the allegations, and didn't remember what I had tried to do for them."
In 2002, Brooke was diagnosed with breast cancer and became a vocal campaigner for raising awareness of the disease in men.
Brooke is one of just nine African-Americans who have ever become senators, including Barack Obama.
Brooke told the Associated Press that he was "thankful to God" that he lived to see Obama elected as the first African-American US president. In 2009, Obama awarded Brooke with the Congressional Gold Medal: the highest award Congress can bestow on civilians.
"Senator Brooke led an extraordinary life of public service," Obama said in a statement. "Ed Brooke stood at the forefront of the battle for civil rights and economic fairness."
Massachusetts Governor Deval Patrick added: "I have lost a friend and mentor."