He was one of the founders of the Kentucky Crippled Children's Commission, serving as president from 1924 to 1941.

He was also a member of the board of charities and correction for the State of Kentucky from 1929 to 1930, and the director of the International Society for Crippled Children.

Williamson was elected as a Democrat to the United States Senate on November 4, 1930, to fill the vacancy caused by the resignation of Frederic M. Sackett and his initial replacement by John M. Robsion.

He served only from December 1, 1930, to March 3, 1931, and was not a candidate for election to a full term.

He died in Cincinnati, Ohio, and was interred in the Ashland Cemetery Mausoleum.