Prolific and versatile character actor William Sanderson was born on January 10, 1944, in Memphis, Tennessee. His mother was an elementary school teacher and his father was a landscape designer. William served two years in the US Army. Following his military service he attended Southern Methodist University. He earned both a BBA degree and a JD law degree from Memphis State University. William went to New York to try his luck as an actor. He studied his craft with Herbert Berghof and William Hickey.
Sanderson appeared as one of the mechanics and regulars of the diner in The Rocketeer, who defies Nazi agents looking for the top secret rocket pack. He also portrayed a character named Deuce in an episode of Babylon 5 and later reprised the role in Babylon 5: Thirdspace. Sanderson voiced Dr. Karl Rossum in Batman: The Animated Series. Sanderson starred in Fight for Your Life, which has a strict ban in the United Kingdom.
As a guest, he made appearances in television shows, and his credits include The Pretender, The X-Files, Knight Rider, Married... with Children, Babylon 5, ER, Coach, and Walker, Texas Ranger. He plays a key role in an audio dramatization of Ursula K. Le Guin's Vaster than Empires and More Slow in NPR's 2000X series. In 2001, Sanderson played the courageous bartender Dewey in the TNT film Crossfire Trail.
Sanderson played Larry in Newhart from 1982 to 1990, famous for the catchphrase, "Hi. I'm Larry. This is my brother Darryl. This is my other brother Darryl."
He returned to television playing E.B. Farnum in the HBO television series Deadwood from 2004 to 2006, later reprising the role in its film continuation. In 2008, Sanderson joined the cast of True Blood, playing Sheriff Bud Dearborne. He played Oldham, the resident interrogation expert of the DHARMA Initiative in an episode of the fifth season of the ABC series Lost.