In the early days of pro football, the NFL and other precursor leagues were a regional phenomenon, limited mostly to the East Coast. and upper Midwest. Result: Unlike today, where teams are based in big cities where big fanbases live, teams back then were based in very, very small towns.
After five years in the early NFL (1920 to 1925) the Rock Island Independents joined an early version of the American Football League in 1926, and folded a year later. They were based in Rock Island, Illinois, which is part of the area called the Quad Cities (which is actually five cities: Rock Island, Moline, and East Moline of Illinois, and Davenport and Bettendorf in Iowa). Population of Rock Island: 39,000.
Tonawanda, New York
Tonawanda is a small suburb of Buffalo, New York. While the Bills play in the metropolis today, the area was represented from 1916 to 1921 by the Tonawanda Lumbermen. The squad, alternately known as the All-Tonawanda All-Stars, and the Lumberjacks, played in the New York Pro Football League before playing a single game in the NFL in 1921 before folding. Population of Tonawanda: 14,000.
Pottsville is a former coal-mining town in eastern Pennsylvania. After a few years as an independent team, the city’s Pottsville Maroons played in the NFL in the late 1920s, before a move to Boston and a name change to the Bulldogs. Population of Pottsville: 14,000.
From 1922 to 1923, the Oorang Indians played in the NFL. In those days, sports teams were often named after their sponsors (the Green Bay Packers were associated with a meat-packing plant, for example). The Oorang Indians were no exception, formed by the owner of Oorang Dog Kennels. The team consisted entirely of Native American players, including the legendary Jim Thorpe, who was also the coach. Like the dog kennel company, the team was based in LaRue, Ohio. Population of LaRue: 700.