O'Fallon is a city along Interstate 70 and Interstate 64 between Lake St. Louis and St. Peters in St. Charles County, Missouri. It is part of the St. Louis Metropolitan Statistical Area. As of the 2010 census O'Fallon had a population of 79,329, making it the largest municipality in St. Charles County and seventh largest in the state of Missouri. In 2006 Money Magazine named O'Fallon 39th in its "Best 100 Places to Live." Money Magazine also ranked O'Fallon 68th out of 100 in 2008 and 26th out of 100 in 2010.