Eugene Beauharnais Beaumont, United States Cavalry officer, the son of Andrew and Julia (Colt) Beaumont, was born in Wilkes-Barre, Luzerne County, Pennsylvania, on August 2, 1837, and appointed to the United States Military Academy at West Point on July 1, 1856. His father had served in the United States Congress from 1832 to 1836 and was descended from a line of Mayflower colonists. His classmates included Confederate major general Thomas L. Rosser of Texas. Beaumont graduated thirty-second in his class and was commissioned a second lieutenant in the First United States Cavalry on May 6, 1861. From then through June he drilled volunteer troops in Washington, D.C., and participated in the battle of First Manassas or Bull Run as a volunteer aide-de-camp to Col. Ambrose E. Burnside in the First Cavalry. After transfer to the Fourth United States Cavalry on August 3, 1861, he served as acting adjutant general of the regiment. He was promoted to first lieutenant on September 14, 1861, and on February 1, 1862, was assigned as aide-de-camp to Gen. John Sedgwick. In this capacity he took part in guarding the upper Potomac River and was engaged in the Peninsular campaign from March through May of 1862. He was posted as aide-de-camp to Gen. Henry W. Halleck on August 7, 1862, but was promoted to captain in the volunteer army and returned to Sedgwick's staff on May 13, 1863. Beaumont served in the Rappahannock campaign with the Army of the Potomac in the spring of 1863 and in the Gettysburg campaign in July. He was brevetted to captain in the regular army on November 7, 1863, for "gallant and meritorious service" in the battle of Rappahannock Station, Virginia. After fighting in the battles of the Wilderness and Spotsylvania, where General Sedgwick was killed in May 1864, Beaumont was transferred as aide-de-camp to Gen. James H. Wilson. He served in the Petersburg campaign and in the Shenandoah valley in the summer of 1864 before transferring with Wilson on October 1 to the cavalry corps of the Army of the Mississippi, where he served as assistant adjutant general. On October 20 he was promoted to major of volunteers. He subsequently saw action in the battle of Nashville (December 1864) and the battle of Harpeth River, Tennessee (December 17, 1864. Beaumont was brevetted lieutenant colonel of volunteers on March 13, 1865, for "gallant and meritorious service" during the pursuit of John Bell Hood's army in Tennessee. On April 2, 1865, his attack on the Confederate breastworks at Selma, Alabama, won him a brevet to major in the regular army and to colonel of volunteers for "gallant and distinguished service." When Confederate president Jefferson Davis was captured in Georgia, he was placed in Beaumont's charge.
At the end of the war Beaumont was mustered out of the volunteer army, on March 19, 1866. He retained his prewar rank in the regular army and was advanced to captain of the Fourth Cavalry on July 25, 1865. He commanded Troop A, which garrisoned San Antonio from April through October 1866 and served at Camp Sheridan, Texas, in November and December. The following months saw him at Fredericksburg, Fort Mason, Fort Chadbourne, and Fort McKavett. After a brief leave of absence he returned to the regiment in May 1869 as commander of the garrison at Lampasas. After recruiting service in 1871 and 1872, he was stationed at Fort Richardson and Fort Clark in 1873 and 1874. On May 18, 1873, he took part in Col. Ranald S. Mackenzie's raid on Kickapoo and Lipan villages at Remolino, Mexico. When Beaumont observed that his officers and men would be "justified in refusing to obey your orders, which you now admit as being illegal, and exposing them to such peril," Mackenzie replied that he would have any officer or man shot who refused to follow him across the Rio Grande. From August 18 through December 29, 1874, Beaumont accompanied Mackenzie on his expedition into Indian Territory after the Warren Wagontrain Raid, and on September 28, 1874, he commanded the advance battalion that attacked Quanah Parker's Comanche encampment in the battle of Palo Duro Canyon.
On March 1, 1875, Beaumont was appointed assistant instructor at the United States Military Academy, where he taught cavalry tactics until August 1879. He was promoted to major on November 12, 1879, and subsequently served in Indian Territory, Colorado, New Mexico, Arizona, and Kansas. On December 24, 1888, he was appointed acting inspector general of Texas, a post that he held until 1892, when he was promoted to lieutenant colonel of the Third United States Cavalry. Beaumont retired from active service on May 16, 1892, and settled at Wilkes-Barre, Pennsylvania. On March 30, 1898, he received the Medal of Honor for his actions at the battle of Harpeth River and at Selma, Alabama, during the Civil War.
He was married to Margaret Rutter on September 18, 1861. She died on April 22, 1879, and he married Maria Lindsley Orton on December 20, 1883. After the death of his second wife on November 19, 1901, he married her sister, Stella S. Orton Rushing, in 1905. Beaumont was the father of four children. According to Robert Goldthwaite Carter, an officer in his regiment, Beaumont was "one of the finest types of an `all around,' efficient" cavalry officer in the army; "with his jet black hair and moustache, soldier's slouch hat, riding pants tucked into his boots, pistols in his belt, and off-hand soldierly way of putting things," Beaumont "favorably impressed" the men of his troop. He died at Harvey's Lake, Pennsylvania, on August 17, 1916.