Lewis Baxter Schwellenbach was born in 1894 in Superior, Wisconsin. His family moved to Washington when he was a young boy, and Schwellenbach attended the University of Washington, ultimately earning a law degree in 1917. After a brief stint in the Army, serving as a private, Schwellenbach was admitted to the Washington state bar in 1919 and joined a Seattle law firm, where he worked for two years before opening his own practice. In 1924, he became chairman of the Democratic State Convention.

In 1932, he sought to become the governor of Washington but was defeated in the Democratic primary. He was more successful in his 1934 bid for the United States Senate and served in Congress until he resigned in 1940 to become the federal district judge of the United States Court for the Eastern District of Washington State. Schwellenbach served as a judge until 1945, when President Harry S. Truman tapped him as his secretary of labor. Lewis Baxter Schwellenbach remained in that position until he died in 1948.