Economic data compiled from official U.S. Census Bureau QuickFacts indicates that the median household income in O'Fallon, Illinois, is approximately USD 105,982, while the mean household income scales higher to about USD 136,093. The per capita income for the city stands at roughly USD 54,265 to USD 62,313 depending on precise sampling metrics. Benefiting from its close proximity to major military and metropolitan employment centers in the St. Louis metropolitan area, O'Fallon boasts a thriving, well-educated population with strong median earnings well above national averages.