Darien is a city in DuPage County, Illinois, United States. Per the 2020 census, the population was 22,011. A southwestern suburb of Chicago, Darien was named after the town of Darien, Connecticut. Darien is just north of I-55 and Historic U.S. Route 66. The entire south edge of the town borders Waterfall Glen.

Interstate 55 (I-55) is a major north–south Interstate Highway in the US state of Illinois that connects St. Louis, Missouri, to the Chicago metropolitan area. It enters the state from Missouri near East St. Louis, Illinois, and runs to U.S. Route 41 near Downtown Chicago, where the highway ends, a distance of 294.38 miles (473.76 km). The road also runs through the Illinois cities of Springfield, Bloomington, and Joliet. The section in Cook County is officially named the Stevenson Expressway, and in DuPage County its officially named the Joliet Freeway or the Will Rogers Freeway. The section from the south suburbs of Chicago to the area near Pontiac is officially named the Barack Obama Presidential Expressway after the 44th President, Barack Obama, who launched his political career from Illinois.