Congress authorizes absentee ballots for Union soldiers, creating federal mail voting

Congress passed legislation in 1864 authorizing Union soldiers to cast absentee ballots in federal elections while serving away from home — the first time federal law permitted voting by mail. At least 19 states also passed their own soldier-voting laws that year. Roughly 150,000 soldiers voted absentee in the 1864 presidential election, with results later credited with helping re-elect Abraham Lincoln.