The battalion was organized 31 December 1861 in the Regular Army at Washington, D.C., from new and existing companies of engineers as a provisional engineer battalion. The battalion participated in major campaigns and battles in the American Civil War to include: Peninsula Campaign (March 1862), Battle of Antietam (September 1862), Battle of Fredericksburg (December 1862), Battle of Chancellorsville (April 1863), Battle of the Wilderness (May 1864), Battle of Spotsylvania Court House (May 1864), Cold Harbor (June 1864), Siege of Petersburg (June 1864-March 1865), and the Confederate surrender after the Battle of Appomattox Court House (April 1865). It was constituted 28 July 1866 as the Battalion of Engineers. The battalion also participated in the War with Spain at the Battle of Santiago in July 1898 and the Philippine Insurrection in 1899. The battalion was then expanded 14 March-7 June 1901 to form the 1st and 2nd Battalions of Engineers.