Flanigan joined the Independents as a backup
end in 1912. For the following two seasons, he served as the team's assistant manager, under then-manager Jack Roche. He then became the manager of the team in 1915. Flanigan soon promoted the Independents by scheduling two games in 1917 against the
Minneapolis Marines, who were the self-proclaimed "North West Pro Champs". This contest would help the Independents gain national attention. Rock Island lost to the Marines by close score of 7–3. However, they were defeated by a wider margin, 33–7, at the second game held in
Minneapolis. However
World War I and the
military draft put a temporary halt to Flanigan's plans of expanding the team into new markets. However once the war ended, Flanigan brought in players from outside the
Rock Island area to build on the team. In 1919, he hired
Rube Ursella of the Marines to serve as a
player-coach. Rube brought several other Minneapolis players with him. These new players would later help get the team an invitation to join the NFL. The Independents lost only to the
Hammond Pros, led by
George Halas in 1919. However, the Independents still had defeated several "
Ohio League" teams that season, such as the
Cincinnati Celts (33–0), the
Columbus Panhandles (49–0) and the
Akron Indians (17–0). Flanigan then challenged the
Canton Bulldogs to a "championship" game, offering a $5,000 guarantee if they would come to Rock Island for the game. However Canton, which had already won the "Ohio League" championship by defeating their arch-rivals, the
Massillon Tigers, turned down the offer. It's likely that Canton's
Jim Thorpe and
Ralph Hay learned that Rock Island's game against the
Akron Indians had drawn only 1,700 spectators and felt that Flanigan could not deliver on his $5,000 guarantee, that was money that came primarily from the gate. However, from Rock Island's viewpoint, the Bulldogs were afraid to play the Independents. That was enough for the Independents to claim the U.S. pro title for themselves. ==Life in the NFL==