Peoria Lake (40°42?8?N 89°33?16?W? / ?40.70222°N 89.55444°W? / 40.70222; -89.55444) is a section of the Illinois River between Peoria in Peoria County, Illinois and East Peoria in Tazewell County, Illinois. The oldest section of Peoria, the largest city on the river, lies at its shores.