( CNN ) -- What was old is new again - at least that 's the way it is for early voting . Before the second Tuesday after the first Monday in November was declared Election Day by federal law in 1845 , states voted on different days and over different periods of time . It was n't until the last decade that early voting began to pick up steam again . In 2004 , 22 % of Americans voted early and that rate rose to more than 30 % in 2008 , according to Paul Gronke , professor of Political Science who founded and runs the Early Voting Information Center at Reed College in Oregon . Gronke estimates that as much as 40 % of eligible voters will cast an early ballot during the 2012 election . With the trend changing the way Americans vote and campaigns campaign , we decided to take a look , by the numbers , at early voting in the United States : . 35 : States ( including the District of Columbia ) that allow early voting . 2 : States with all mail-in voting . Washington and Oregon do n't have traditional polling places . Early voting surge suggests Democratic push pays off in Iowa . 28 : Percent of Florida voters who said in 2004 they preferred early voting because of the convenience . 30 : Percent who said they did n't feel like standing in a long line to vote . In voting , the early bird skips the line . 46.5 : Percent of Nevada voters who voted early in 2008 . 45 : Minimum number of days before the election that absentee ballots must be sent to military service members overseas , according to the Uniformed and Overseas Citizens Absentee Voting Act , which was enacted in 1986 . 3 : Days before the election set aside for Ohioans to vote in person . The Supreme Court rejected an appeal to block early voting . 15 : States which voiced support for the Ohio Secretary of State Jon Husted , who was named in the lawsuit . John King : Who benefits from early voting ? 2 : Number of months before the election someone in North Carolina can vote . September 7 was the earliest start date for absentee voting in the United States . 30.3 : Percent of voters nationwide who voted early in 2008 . 10 : Percent increase in early voting from 2006 to 2008 . 26 million : Absentee ballots sent out by states in 2008 . 8.12 million : The estimated number of people who have already voted as of October 25 , according to Michael McDonald of the United States Election Project at George Mason University . 91 : Percent of domestic mailed ballots that were returned in 2008 . CNN 's Allison Brennan , Adam Levy and Robert Yoon contributed to this report .
2 : Number of states with all mail - in voting . 3 : Days before the election set aside for voters to vote in person . 30.3 : Number of voters nationwide who voted early in 2008 . 8.12 million : The estimated number of people who have already voted as of October 2008 .