Waukegan is a city and county seat of Lake County, Illinois. It is the ninth-largest city in Illinois by population. It is the fifth-largest city on the western shore of Lake Michigan, after Chicago, Milwaukee, Green Bay, and Kenosha. According to the United States Census Bureau, the city has a total area of 23.1 square miles (59.8 square kilometer). 23.0 square miles (59.6 square kilometer) of it is land and 0.1 square miles (0.2 square kilometer) of it (0.35%) is water.