 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.After flowing through the swamp, it flows northward, across the escarpment in a series of waterfalls and rapids at Shelby Center, thence passing through the Village of Medina to the small Glenwood Lake north of the village.