For the first century or so of American independence, people stayed close to home and voted in person at the nearest polling station—much like we do today. As NBC News reports, there were a couple early exceptions to this tradition. In 1775, the town of Hollis, New Hampshire, permitted Continental Army soldiers to send representatives to vote in their stead at a local meeting; and Pennsylvania let soldiers send in their ballots during the War of 1812, though the practice was later declared unconstitutional.
But those scattered instances weren’t enough to make absentee voting a matter of national significance. During the Civil War, however, things changed. If all the Union soldiers stationed away from home couldn’t vote in the presidential election of 1864, it could potentially affect the outcome. Thinking that the majority of those soldiers would support Republican incumbent Abraham Lincoln over Democrat George McClellan, the Republican Party began lobbying for laws allowing far-flung soldiers to cast their ballots from the battlefield.