Robert L. Mouton was born in Duchamp on October 20, 1892 in St. Martin Parish, Louisiana. Mouton moved with his parents to Lafayette, where he attended public schools. He graduated from Southwestern Louisiana Institute (now University of Louisiana at Lafayette). During WWI, Mouton enlisted in the United States Marine Corps, serving as an interpreter and intelligence officer attached to the first squadron of the first marine aviation outfit overseas from May 1918 to January 1919.

After the war, Mouton returned to Lafayette and engaged in horticultural pursuits. He served as mayor of Lafayette from 1919-1927 and 1931-1935. He was a postmaster from May 1929 until November 1930. He served as a member of the United States Marine Corp Reserve with rank of captain. He was a delegate to the 1936 Democratic National Convention, and was elected as a Democrat to the 75th and 76th Congresses, January 3, 1937 – January 3, 1941. He died in New Orleans on November 26, 1956. He was interred at St. John’s Catholic Cemetery, Lafayette.