High Quality Content by WIKIPEDIA articles! O`Fallon is a neighborhood of St. Louis, Missouri. The neighborhood is located on the north side of the City of St. Louis, nestled between O’Fallon Park and Fairgrounds Park. It is bounded by West Florissant, Harris Avenue, Algernon Street and Adelaide on the north, Pope Avenue on the northwest, Kossuth and Natural Bridge Avenues on the south via Fair Avenue, Warne on the east, and Newstead on the west.