Joliet (/ˈdʒoʊli.ɛt/ or /dʒoʊliˈɛt/) is a city in Will and Kendall counties in the U.S. state of Illinois, located 40 miles (64 km) southwest of Chicago. It is the county seat of Will County. As of the 2010 census, the city was the fourth largest in Illinois, with a population of 147,433, which was estimated to have increased to 147,806 by July 2013. It continues to be Illinois's fastest growing city. When Joliet was first planned in the early 1830s, it was still in Cook County.