O'Fallon is a city in St. Clair County, Illinois, United States. The 2020 census listed the population at 32,289. The city is the second largest city in the Metro-East region and Southern Illinois. It sits 5 miles from Scott Air Force Base and 18 miles from Downtown St Louis.
Like its namesake in St. Charles County, Missouri, O'Fallon is part of the St. Louis Metropolitan Statistical Area. This makes O'Fallon one of the few pairs of like-named municipalities to be part of the same MSA.
Wikipedia https://en.wikipedia.org/wiki/O'Fallon,_Illinois
Coordinates 38°35'32.177" N -89°54'40.365" E
