Byrd's foster father was a miner who frequently changed jobs, and Byrd recalled that the family's house was "without electricity, ... no running water, no telephone, a little wooden outhouse."
He graduated from high school but could not afford college. Married in 1936 to high school sweetheart Erma Ora James — with whom he had two daughters — he pumped gas, cut meat and during World War II was a shipyard welder.
Returning to meat cutting in West Virginia, he became popular for his fundamentalist Bible lectures. A grand dragon of the Ku Klux Klan suggested he run for office.
He won his first race — for the state's House of Delegates — in 1946, distinguishing himself from 12 rivals by singing and fiddling mountain tunes. His fiddle became a fixture; he later played it on the television show "Hee Haw" and recorded an album. He abandoned it only after a grandson's traumatic death in 1982 and when his shaky hands left him unable to play.
At his 90th birthday party in 2007, however, Byrd joined bluegrass band Lonesome Highway in singing a few tunes and topped off the night with a rendition of "Old Joe Clark."
After six years in the West Virginia legislature, Byrd was elected to the U.S. House in 1952 in a race in which his brief Klan membership became an issue. He said he joined because of its anti-communism.
Byrd entered Congress as one of its most conservative Democrats. He was an early supporter of the Vietnam War, and his 14-hour, 13-minute filibuster against the 1964 civil rights bill remains one of the longest ever. His views gradually moderated, particularly on economic issues, but he always sided with his state's coal interests in confrontations with environmentalists.
His love of Senate traditions inspired him to write a four-volume history of the chamber. It also led him to oppose laptops on the Senate floor and to object when a blind aide tried bringing her seeing-eye dog into the chamber.
In 2004, Byrd got Congress to require schools and colleges to teach about the Constitution every September 17, the day the document was adopted in 1787.