Union forces stopped the Confederate invasion of Maryland at the Battle of Antietam on September 17, 1862, still the bloodiest day in American history. When news first came of the Confederate Army's movement, Pennsylvania Governor Andrew Curtin declared a state of emergency and called for the enlistment of 50,000 state troops to assemble at Harrisburg. Transporting troops and military supplies from Harrisburg to northern Maryland fell especially hard on the limited resources and single track of the Cumberland Valley Railroad. After Antietam, many state militia troops who had gone south for the fight returned home by way of the Cumberland Valley Railroad, and the Union Army continued to use it heavily to service a supply depot established in Hagerstown, Maryland.