Washington Lafayette Elliott was born in Carlisle, Pennsylvania on March 31, 1825. He was the son of Commodore Jesse Duncan Elliott, USN. Before he reached his teens, young Washington accompanied his father on cruises with the West Indies Squadron and on board the USS Constitution, which his father commanded in the Mediterranean for a time. For several years, Commodore Elliott was also a trustee of Dickinson College. The younger Elliott was enrolled in the Grammar School there in 1838, then completed two years as an undergraduate with the class of 1843.
In June 1841, Washington Elliott was appointed as a cadet at West Point. He studied medicine for a period, then took a commission in May 1846 as a second lieutenant of mounted infantry at the outbreak of the Mexican War. Elliott served at Vera Cruz and was appointed full lieutenant in July 1847. He then served at Fort Laramie on the Oregon Trail in Wyoming (1849-1851) and in Texas (1852-1856), receiving a promotion to captain in 1854. Elliott also held assignments in New Mexico during the five years preceding the Civil War, gaining ample experience as a frontier soldier in skirmishes against the Comanche and Navajo tribes.
During the Civil War, Elliott distinguished himself at Wilson's Creek in Missouri and was appointed colonel in command of the Second Iowa Cavalry in September 1861. In November, he was promoted to the permanent rank of major and was nominally assigned to the First U.S. Cavalry Regiment. Elliott was given command of a brigade in the Army of Tennessee and won a brevet for gallantry in the capture of Island No. 10 in the Mississippi. During the spring of 1862, he distinguished himself again in a long cavalry raid into Mississippi, the first such Union action of the war. In this raid, Elliott led a brigade of Iowa and Michigan cavalry against the communications of the Mississippi and Ohio Railway.
Elliott was promoted to temporary brigadier general in June 1862, and his efforts as a Union commander were unceasing for the remainder of the conflict. He was wounded at Second Bull Run while serving as division commander in the Armies of the Potomac and the Cumberland, in which he became chief of cavalry. Elliott also participated in the march on Atlanta and fought at the Battle of Nashville. By that time, he was a major general of volunteers and a brevet regular brigadier general. At the end of the war, Elliott was breveted as a regular major general and received permanent promotion to lieutenant colonel of cavalry in August 1866. He then returned to duty in the western territories. Elliott served in Oregon and California toward the end of his military career and was promoted to full colonel in April 1878. A year later, he retired and took up a civilian career as a banker in San Francisco. Washington Lafayette Elliott died in that city on June 29, 1888. He was sixty-three years old.