Henry Warner Slocum, Sr. (September 24, 1827 – April 14, 1894), was a Union general during the American Civil War and later served in the United States House of Representatives from New York. During the war, he was one of the youngest major generals in the Army and fought numerous major battles in the Eastern Theater and in Georgia and the Carolinas. While commanding a regiment, a brigade, a division, and a corps in the Army of the Potomac, he saw action at First Bull Run, the Peninsula Campaign, South Mountain, Antietam, Chancellorsville, and Harpers' Ferry.