Union soldiers vote by mail in 1864 presidential election first large-scale absentee voting in US

Following advocacy from President Lincoln and Secretary of War Edwin Stanton, Union Army soldiers vote by absentee ballot from the field in the 1864 presidential election, the first large-scale instance of mail voting in U.S. history. Pennsylvania had become the first state to allow soldier absentee voting during the War of 1812. Over 3 million absentee ballots are eventually cast during the Civil War era. Lincoln wins reelection. The military vote is credited with providing his margin of victory in several states.