The CommonCensus NFL FAN Map

The National Football League (NFL) is the highest level of professional American football in the United States. It was formed by eleven teams in 1920 as the American Professional Football Association, with the league changing its name to the National Football League in 1922. The league currently consists of thirty-two teams from the United States. The league is divided evenly into two conferences — the American Football Conference (AFC) and National Football Conference (NFC), and each conference has four divisions that have four teams each, for a total of 16 teams in each conference. The NFL is organized as an unincorporated association of its 32 teams.^[1][2] The NFL is by far the most attended domestic sports league in the world by average attendance per game, with 67,509 fans per game in the latest regular season (2009).^[3]

The regular season is a seventeen-week schedule during which each team plays sixteen games and has one bye week. The season currently starts on the Thursday night in the first full week of September (the Thursday after Labor Day) and runs weekly to late December or early January. At the end of each regular season, six teams from each conference (at least one from each division) play in the NFL playoffs, a twelve-team single-elimination tournament that culminates with the championship game, known as the Super Bowl. This game is held at a pre-selected site which is usually a city that hosts an NFL team.

http://en.wikipedia.org/wiki/National_Football_League