Clark Wallace Thompson, politician and military leader, was born on August 6, 1896, in LaCrosse, Wisconsin, the son of Clark Wallace and Jesse Marilla (Hyde) Thompson. He grew up in Oregon and from 1915 to 1917 attended the University of Oregon, where he was a member of Phi Delta Theta. On May 25, 1917, he enlisted in the United States Marine Corps. After basic training he was stationed at Fort Crockett in Galveston, Texas, where he met Libbie Moody, daughter of William L. Moody, Jr. He was discharged from the marines as an enlisted man on December 15, 1918, and commissioned a second lieutenant in the marine reserves on December 16, 1918. Thompson married Libbie in Richmond, Virginia, on November 16, 1918. They had two children. Shortly after he was commissioned the Thompsons moved to Galveston. In 1919 Thompson became treasurer of the American National Insurance Company. In 1920 he left that business to open a mercantile firm, Clark W. Thompson Company, which he owned until 1932. In 1927 he became involved in the Cedar Lawn Development Company; he served as its secretary-treasurer until 1934. He was appointed public relations counsel for the Moody interests in 1936 and served until 1947, when he was elected to the United States House of Representatives. Thompson's real love was the United States Marine Corps. Continuing his connection with the corps as a member of the reserve, Thompson organized the Fifteenth Battalion of the USMC Reserves in 1936. He was called up to national service in 1940, attended the Naval War College in 1941, and in 1942 was sent to the Southwestern Pacific Theater with his unit; he was the oldest officer in his theater. In 1943 he was returned to Washington, D.C., to become director of the marine reserves, a position he held until he retired as a colonel in 1946. He was awarded the Legion of Merit for his service.
Thompson's concern with national defense led him into politics. In 1933 he was elected to represent the Seventh (later the Ninth) Texas Congressional District to fill the seat left vacant by Clay Stone Briggs. He made a mark with his legislative efforts to strengthen the military before he was redistricted and chose to step down. He was elected in 1946 to the same seat, on the death of Joseph Jefferson Mansfield, and held it until he retired on January 3, 1967. In the Congress he was a member of the Agricultural, Maritime and Fisheries, and Ways and Means committees. He and his wife were also an important part of the Washington, D.C., social scene; their home was known as the "Texas Embassy" or "Texas Legation," a central feature in the life of Washington during the 1950s and 1960s. Thompson played an important role in bridging the gap between different factions of the state Democratic party. In 1968, after retiring from the House, he became legislative consultant for Hill and Knowlton and director of the Washington office of Tenneco. Thompson was a member of the Episcopal Church. He was president of the Galveston Chamber of Commerce in 1931 and 1935–36 and a member of the American Legion, the Veterans of Foreign Wars, and the Texas State Society; he was also a thirty-second-degree Mason and a Shriner. He died in Galveston on December 16, 1981, and was buried in Galveston Memorial Cemetery. His papers are in the Baylor University Library.