Lois Capps was born in Ladysmith, Wisconsin as the daughter of a Lutheran minister. She has lived in Santa Barbara, California since 1960. She was educated at Pacific Lutheran University with a bachelor's degree in nursing. She earned a master's degree in religion at Yale University and a master's degree in education at the University of California, Santa Barbara. While at Yale, she married Walter Capps, a divinity student at Yale who later became a famous religious studies professor at UCSB. She worked for 20 years as a nurse and health advocate for the Santa Barbara public schools and also taught early childhood education part-time at Santa Barbara City College.

Walter Capps was elected to Congress in 1996 in a rematch of his 1994 race against Republican Andrea Seastrand. However, he died of a heart attack on October 28, 1997, only nine months into his term. His widow then won the then-22nd District seat by defeating Republican Tom Bordonaro in a special election on March 10th, 1998. She was sworn into the 105th Congress on March 17th. Capps successfully defended her seat against the same opponent in a general election later that year, and commenced her first full term in office. In 2000, Capps retained her seat, defeating Republican Mike Stoker with 53f the vote. She was the first Democrat to hold the district for more than one term in over 50 years (the district, known as the 11th from its formation in 1943 until 1953, the 13th from 1953-75 and the 19th from 1975-93) had been held by Republicans from 1947 until Walter Capps' victory in 1994). Redistricting made Capps somewhat safer, and she was reelected without serious opposition in 2002 and 2004.