Located in the state of Missouri and a city in St. Charles County, O’Fallon forms part of the St. Louis Metropolitan Statistical Area and has a population of more than 80.000 that made it the largest municipality in the county of St. Charles. It is interesting to note that O’Fallon’s namesake in St. Charles County, Illinois, also forms part of the St. Louis Metropolitan Statistical Area. In 1856, Nicolas Krekel founded O’Fallon and the name was named after John O’Fallon, the then president of the North Missouri Railroad.