Known for its vast Tallgrass prairies, DuPage County has become mostly developed and suburbanized, although some pockets of farmland remain in the county's western and northern parts. Located in the Rust Belt, the area is one of few in the region whose economy quickly became dependant on the headquarters of several large corporations due to its close proximity to Chicago. As steel mills closed in the 1970's and 80's, several acres that were formally industrialized areas were converted into business parks to meet the growing tax base. The county has a mixed socioeconomic profile and residents of Hinsdale, Naperville and Oak Brook include some of the wealthiest people in the Midwest. However, in other cities, such as Aurora, Downers Grove and Darien, the loss of manufacturing jobs over the past 30 years has resulted in higher-than-average crime rates compared to the municipalities they border. On the whole, the county enjoys above average median household income levels and low overall poverty levels when compared to the national average. In 2018, Niche ranked two DuPage municipalities (Clarendon Hills #3 and Naperville #16) amongst the top 20 best places to live in America.