The northern border of the county is Tonawanda Creek. Part of the southern border is Cattaraugus Creek. Other major streams include Buffalo Creek (Buffalo River), Cayuga Creek, Cazenovia Creek, Scajaquada Creek, Eighteen Mile Creek and Ellicott Creek. The county's northern half, including Buffalo and its suburbs, is known as the Northtowns and is relatively flat and rises gently up from the lake. The southern half, known as the Southtowns, is much hillier. It has the northwesternmost foothills of the Appalachian Mountains. The highest elevation in the county is a hill in the Town of Sardinia that tops out at around 1,940 feet (591 m) above sea level. The lowest ground is about 560 feet (171 m), on Grand Island at the Niagara River. The Onondaga Escarpment runs through the northern part of Erie County.