Henry Garland Dupré was born on 28 July 1873 in Opelousas, Louisiana. He was the eldest son of Marie Celeste Garland and Laurent Dupré. He attended Tulane University and graduated with a law degree in 1892. He was admitted to the bar and began practice in New Orleans in 1895. He was never married. He died 21 February 1924and was interred in the Dupré family vault, Catholic Cemetery, Opelousas, Louisiana. One of his sisters was Edith Garland Dupré, who was a member of the first faculty at Southwestern Louisiana Industrial Institute.

Dupré served in the Louisiana legislature and the U.S. House of Representatives. He was a member of the Louisiana House of Representatives from 1900-1910. On 8 November 1910, he was elected to a seat in the U.S. House of Representatives where he served until his death. He had extensive knowledge of parliamentary law and served on the Judiciary Committee and the Rivers of Harbor Committee.