Much of the Midway area is former marshland which has been filled in for development. In fact, the San Diego River used to flow through the Midway area into San Diego Bay, isolating Point Loma from San Diego. Because of fears that San Diego Bay might silt up, the river was diverted to its present course north of Point Loma by a levee built in 1877. Parts of Liberty Station and Point Loma Village are also fill land, reclaimed from sand spits and wetlands surrounding the Bay. The only remnant of the formerly extensive wetlands in Point Loma, aside from the riverbed itself, is a city-owned nature preserve called Famosa Slough, which branches off from the river near its mouth.