Oak Orchard Creek rises south of Oak Orchard Creek Marsh (also called the "Alabama Swamp") at the border of Orleans and Genesee counties. The swamp contains a state reserve, Oak Orchard Wildlife Management Area, and a national reserve, the Iroquois National Wildlife Refuge, both of which are known as major stopover points for migratory birds. Oak Orchard Creek Marsh was designated a National Natural Landmark in May 1973. The swamp is a result of a partial blockage of the river by glacial drift and an outcrop of limestone and dolomite known as the Lockport Formation which forms the Niagara Escarpment.