Thomas Hennings was born in St. Louis, Missouri, on 25th June, 1903. After graduating from Cornell University (1924) and Washington University (1926) he worked as a lawyer in St. Louis.

Henning's served as assistant circuit attorney (1929-34) and lecturer on criminal jurisprudence at the Benton College of Law (1934-1938).

A member of the Democratic Party Hennings was elected to Congress in 1935. However, he resigned to become circuit attorney for St. Louis in 1941. During the Second World War Hennings served as a lieutenant commander of the United States Naval Reserve (1941-1943).

Henning's was elected to the Senate in 1950. He became chairman of the Committee on Rules and Administration. Thomas Hennings remained in the Senate until his death on 13th September, 1960.