Voting by mail can trace its roots to soldiers voting far from home during the Civil War and World War II. By the late 1800s, some states were extending absentee ballots to civilian voters under certain conditions, but it wasn’t until 2000 that Oregon became the first state to move to an all-mail voting system. Here is everything you need to know about the history of absentee voting and vote by mail.

What Does the Constitution Say About Voting?

There is no step-by-step guide to voting in the United States Constitution. Article 1, Section 4 says that it’s up to each state to determine “The Times, Places and Manner of holding Elections.” This openness has enabled the voting process in the United States to evolve as the country’s needs have changed.

The Founding Fathers voted by raising their voices—literally. Until the early 19th century, all eligible voters cast their “Viva Voce” (voice vote) in public. While the number of people eligible to vote in that era was low and primarily composed of land-owning white males, turnout hovered around 85 percent, largely due to enticing voting parties held at polling stations.

The first paper ballots appeared in the early 19th century and were originally blank pieces of paper. By the mid-1800s, they had gone to the other extreme: political parties printed tickets with the names of every candidate pre-filled along party lines. It wasn’t until 1888 that New York and Massachusetts became the first states to adopt pre-printed ballots with the names of all candidates (a style called the “Australian ballot” after where it was created). By then, another revolution in voting had taken place: Absentee voting.

The Civil War and Absentee Ballots

The first widespread instance of absentee voting in the United States was during the Civil War. The logistics of a wartime election were daunting: “We cannot have free government without elections,” President Abraham Lincoln told a crowd outside the White House in 1864, “and if the rebellion could force us to forgo, or postpone a national election, it might fairly claim to have already conquered and ruined us.”

“Lincoln was concerned about the outcome of the midterm elections,” says Bob Stein, Director of the Center for Civic Leadership at Rice University. “Lincoln’s Secretary of War, Edwin Stanton, pointed out that there were a lot of Union soldiers who couldn’t vote, so the president encouraged states to permit them to cast their ballots from the field.” (There was some precedent for Lincoln’s wish; Pennsylvania became the first state to offer absentee voting for soldiers during the War of 1812.)

In the 1864 presidential election between Lincoln and George McClellan, 19 Union states changed their laws to allow soldiers to vote absentee. Some states permitted soldiers to name a proxy to vote for them back home while others created polling sites in the camps themselves. Approximately 150,000 out of one million soldiers voted in the election, and Lincoln carried a whopping 78 percent of the military vote.

By the late 1800s, several states offered civilians the option of absentee voting, though they had to offer an accepted excuse, most commonly distance or illness. The passage of the 15th Amendment in 1870 and 19th Amendment in 1920 expanded the number of eligible voters in the United States, but it would take another war to propel absentee voting back into the national spotlight.

Read more on The History Channel.