Farmhouse sandwiches is Minutes west of St. Louis County on highway K near O’Fallon Rd the City of O'Fallon encompasses nearly 30 square miles with ideal access to I-70 in the north and I-64 in the south. O'Fallon is the seventh largest city in Missouri and largest in St. Charles County, with a growing population of approximately 76,000 residents. The City today offers the latest in housing, business, retail and leisure. Call today to learn more.