Thor Tollefson was born in Perley, Minnesota on May 2, 1901. He was the oldest of seven children. His family moved to Tacoma when he was ten years old, and when his father died, he dropped out of school to go to work and support his mother and siblings at the age of fourteen. After seven years of working in the lumber mills he went back to school and graduated from Lincoln High in 1924. He then went on to the University of Washington and graduated from law school in 1930. He married Eva Tollefson in 1934 and they had three daughters.

After opening a private law practice, Tollefson was elected Pierce County Prosecutor in 1938 and served in that office until 1946, when he was elected to the U.S. House of Representatives as a Republican for the 6th congressional district. He served nine terms in Congress, until he was defeated for re-election in 1964. As a congressman he served as chairman of the House Committee on Merchant Marine and Fisheries and was twice appointed U.S. delegate to the Interparliamentary Union. After leaving Congress he was appointed Director of the Fisheries Department for Washington state by Governor Dan Evans in 1965. He retired from the department in 1975 and passed away on December 30, 1982 at the age of 81 years old.