Naperville is a city in DuPage and Will counties in the U.S. state of Illinois, and a suburb of Chicago. In a 2010 study assessing cities with populations exceeding 75,000, Naperville was ranked as the wealthiest city in the Midwest and the eleventh wealthiest in the nation. It was ranked among the nation's safest cities by USAToday and Business Insider.Naperville was voted the second-best place to live in the United States by Money magazine in 2006 and it was rated first on the list of best cities for early retirement in 2013 by Kiplinger. As of the 2010 census, the city had a population of 141,853, which was estimated to have increased to 147,112 by July 2015. It is the fifth-largest city in Illinois.