Football, also known as gridiron or American football outside of North America, attracts more television viewers than baseball (although baseball attracts significantly more ticket sales due to its much longer schedule). Despite being entirely male, it has the most participants of any sport at both high school and college (NCAA) levels.
The NFL is the preeminent professional league in the United States. Through expansion teams and the landmark merger with the American Football League in 1970, the NFL has reached its current mark of 32 franchises divided into two conferences. After a 16-game regular season, each conference sends six teams to the NFL Playoffs, which eventually culminate in the league's championship game, the Super Bowl.
Super Bowl Sunday is the biggest annual sporting event held in the United States. The Super Bowl itself is always among the highest-rated programs annually in the Nielsen ratings. Some notable former players include Joe Montana, Jim Brown, Roger Staubach, Brett Favre, Dick Butkus, Terry Bradshaw, Dan Marino, Troy Aikman, Otto Graham, Emmitt Smith, Barry Sanders, John Elway, Jerry Rice, Fran Tarkenton, Kurt Warner, Johnny Unitas and Lawrence Taylor. Some notable current NFL players include Peyton Manning, Drew Brees, Ray Lewis, Tony Romo, Tom Brady, Brian Urlacher, Adrian Peterson, Aaron Rodgers, Eli Manning, Michael Vick, Jared Allen, Ben Roethlisberger, and Donovan McNabb.
Additionally millions also watch college football throughout the fall months, and some communities, particularly in rural areas, place great emphasis on their local high school football team. The popularity of college and high school football in areas such as the Southern United States and the Great Plains stems largely from the fact that these areas historically generally didn't possess markets large enough for a professional team. Nonetheless, college football has a rich history in the United States, predating even the NFL, and fans and alumni are generally very passionate about their teams.
Arena football, a form of football played in indoor arenas, has a professional league, the Arena Football League. The original league was active from 1987 to 2008 and folded in 2009, but several teams from the AFL and its former minor league, af2, relaunched the league in 2010. Several semi-professional leagues, mostly regional in nature, also exist.