Allen Thomas was born December 14, 1830, in Howard County, Maryland. He graduated from Princeton University in 1850 and became a lawyer. After his marriage, in 1857, he moved to Louisiana where he became a planter and a colonel in the Louisiana militia. He was a brother-in-law of Confederate Lieutenant GeneralRichard Taylor.
Allen Thomas joined the 29th Louisiana Infantry as a major in July 1861. On May 3, 1862, he was promoted to colonel of the regiment, when it was expanded from its original battalion size. He commanded a brigade in the Confederate Department of Mississippi and East Louisiana in December 1862 and January 1863. He fought in the Vicksburg Campaign, notably at the Battle of Chickasaw Bayou. During the siege of Vicksburg, Thomas and his regimental staff occupied Planters Hall, a building which survives and is listed on the U.S. National Register of Historic Places. Thomas was captured in the fall of Vicksburg on July 4, 1863, and was later exchanged. After his parole, he brought Lieutenant General John C. Pemberton's report on the fall of Vicksburg to Richmond. He then served in reorganizing paroled and exchanged prisoners. Thomas was promoted to brigadier general on February 4, 1864. He was assigned to the department of his brother-in-law, Lieutenant General Richard Taylor, at Alexandria, Louisiana, where he commanded a brigade of five Louisiana regiments and a battalion. From September 1864 to May 26, 1865, with the exception of March 17, 1865, to May 10, 1865, when he commanded the division of Major GeneralCamille Armand Jules Marie, Prince de Polignac when Polignac went to France to seek help for the Confederacy from Napoleon III, Thomas commanded a brigade in Polignac's division in the Confederate Army of the Trans-Mississippi. Allen Thomas was paroled at Natchitoches, Louisiana, on June 8, 1865, and pardoned on July 19, 1865.
Aftermath
After the Civil War, Thomas returned to his plantation. He became a professor of agriculture and member of the board of supervisors at Louisiana State University in 1882-1884. He was a Presidential elector in 1872 and 1880. Then he became coiner at the United States Mint at New Orleans. Thomas was nominated to run for Congress in 1876 but declined. In 1889, he moved to Florida. He was U.S. Minister to Venezuela from 1895 to 1897, succeeding Seneca Haselton. Thomas moved to Waveland, Mississippi, where he had bought a plantation, in 1907 and died there on December 3, 1907. Allen Thomas was buried at Ascension Catholic Church Cemetery, Donaldsonville, Louisiana, in the family vault of his wife.
