Bellefontaine Neighbors is an inner-ring suburban city in St. Louis County, Missouri, United States. The population was 10,740 at the 2020 census. The history of Bellefontaine Neighbors, Missouri, can be traced back to the mid-1800s when the area was part of the Louisiana Territory, which was ceded by France to Spain in 1762 in the Treaty of Fontainebleau. Spanish military authorities constructed forts near the mouth of the Missouri River to strengthen their hold on the territory and discourage intruders from the east. A Captain Rios, who was dispatched to the area, established forts near the present-day locations of Spanish Pond and Fort San Carlos in St. Louis.