Alfred Pleasonton (June 7, 1824 – February 17, 1897) was a United States Army officer and major general of volunteers in the Union cavalry during the American Civil War. He commanded the Cavalry Corps of the Army of the Potomac during the Gettysburg campaign, including the largest predominantly cavalry battle of the war, Brandy Station. In 1864, he was transferred to the Trans-Mississippi theater, where he defeated Confederate General Sterling Price in two key battles, including the Battle of Mine Creek, the second largest cavalry battle of the war, effectively ending the war in Missouri. He was the son of Stephen Pleasonton and younger brother of Augustus Pleasonton. Early life Pleasonton was born in Washington, D.C., on June 7, 1824. He was the son of Stephen and Mary Hopkins Pleasonton. Stephen was well known at the time of Alfred's birth. During the War of 1812, as a U.S. State Department employee, he saved crucial documents in the National Archives from destruction by the British invaders of Washington, including the original Declaration of Independence and the U.S. Constitution. As Fifth Auditor of the U.S. Treasury, Stephen Pleasonton was the de facto superintendent of lighthouses of the United States from 1820 to 1852. His conservative approach and emphasis on the economy held back advancements in lighthouse construction and technology and led to the deterioration of some lighthouses. Since he had no technical knowledge of the field, he delegated many responsibilities to local customs inspectors. In 1852, the U.S. Congress decided reform was needed and established the Lighthouse Board to take over fiscal and administrative duties for U.S. lighthouses. Alfred's much older brother, Augustus, attended the United States Military Academy and served as Assistant Adjutant General and paymaster of the state of Pennsylvania; his career direction obviously affected his younger brother's and both boys were assured nomination to the Academy by their father's fame from the War of 1812. Alfred graduated from West Point on July 1, 1844, and was commissioned a brevet second lieutenant in the 1st U.S. Dragoons (heavy cavalry). He was stationed first at Fort Atkinson, Iowa. He followed his unit for frontier duty in Minnesota, Iowa, and Texas. He was promoted to second lieutenant with the 2nd U.S. Dragoons on November 3, 1845. With the 2nd Dragoons, he fought in the Mexican–American War and received a brevet promotion to first lieutenant for gallantry in the Battle of Palo Alto