The 37^th and 38^th Congresses (1861–1865) played an active role during the Civil War through legislation, appropriations, and oversight. In 1861, Congress encouraged development of the ironclad warship. The U.S.S. Monitor, designed by Swedish-American engineer John Ericsson, was tested in an encounter with the Merrimac, a Union ship the Confederates had captured, fitted with iron armor, and renamed the C.S.S. Virginia. Their March 9, 1862 battle at Hampton Roads, Virginia—the world’s first between steam-powered ironclads—revolutionized naval warfare.