Illinois is the sixth most populous state in the U.S. with a population that is quickly approaching 13 million people. Surprisingly, this reflects negative growth between estimates from 2016 and 2017. Chicago is the most populous city in the state, posting an estimated 2.7 million people per 2017 estimates. This far exceeds the population of the second most populated city, Aurora, which has just over 200,000 people according to estimates. There are 1,299 incorporated municipalities in Illinois, which includes cities, towns and villages. There is a total of 102 counties within the state.
Of the incorporated cities, the least populous is Nason, located in Jefferson County. Nason has a population of just 236 people. There are multiple municipalities within the state that have a population of less than 1,000, including Orient in Franklin County, Creal Springs in Williamson County and Grand Tower in Jackson County. The state has a total of seven cities with populations that exceed 100,000, and 192 cities with populations between 10,000 and 100,000 people.