Short answers, pulled from the story.
Pudge Heffelfinger signed a contract for $500 to play for the Allegheny Athletic Association in 1892, marking the first recorded instance of an American football player receiving pay. John Brallier became the first open professional when he took $10 to play for the Latrobe Athletic Association.
The league changed its name to the National Football League in 1922 after teams from other regional circuits joined the original American Professional Football Conference formed in 1920. The Akron Pros held the best record in 1920 while the Chicago Staleys were named champions in 1921 despite controversy.
The Arizona Cardinals are the oldest existing professional football club which has operated near-continuously since 1913. Their history traces back to a team that played from 1898 to 1906 on Racine Street in Chicago.
The Arena Football League began its 24th season in 2011 and folded again after its 2019 season following a steady decline from 18 teams in 2011 to four teams in 2018. A minor league called AF2 ran for 10 seasons from 2000 to 2009 before the current version collapsed under bankruptcy after the 2008 season.
NBC broadcast the first-ever televised professional football game from Ebbets Field on the 22nd of October 1939. Two fixed monochrome iconoscope cameras captured the contest between the Brooklyn Dodgers and the Philadelphia Eagles with a single play-by-play commentator named Skip Walz.