Short answers, pulled from the story.
The Rock Island Independents hosted the first official National Football League game on the 26th of September 1920 at Douglas Park in Rock Island, Illinois. They defeated the St. Paul Ideals 48-0 in front of 800 fans, just nine days after the league had formed.
Demetrius Clements founded the Rock Island Independents in 1907 as an independent football club with no athletic club, social club, or corporate backing. The name Independents reflected that freestanding status.
Five Pro Football Hall of Famers played for the Independents: Jimmy Conzelman (1920-1921), Joe Guyon (1924), Ed Healey (1920-1922), Duke Slater (1922-1926), and Jim Thorpe (1924-1925).
Owner Dale Johnson moved the team to the new American Football League in 1926, believing the AFL's association with football star Red Grange would make it more successful than the NFL. The Independents were the only NFL franchise to join the rival league.
After the AFL folded at the end of the 1926 season, the Independents were rejected in their attempt to rejoin the NFL. They played as a semi-pro team in 1927, then went out of business.
The Rock Island Independents posted an overall NFL record of 26-14-9 across six seasons, with five winning seasons. Their best finish in the NFL standings was fifth place, achieved in 1921, 1922, and 1924.