St. Charles is a city in DuPage and Kane counties in the U.S. state of Illinois. It lies roughly 40 miles (64 km) west of Chicago on Illinois Route 64. Per the 2020 census, the population was 33,081. The official city slogan is "Pride of the Fox", after the Fox River that runs through the center of town. St. Charles is part of a tri-city area along with Geneva and Batavia, all western suburbs of similar size and socioeconomic condition.