Sterling is a city in Whiteside County, Illinois, United States, along the Rock River. The population was 14,782 at the 2020 census, down from 15,370 in 2010. Formerly nicknamed "Hardware Capital of the World", the city has long been associated with manufacturing and the steel industry.

Whiteside County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 55,691. Its county seat is Morrison. The county is bounded on the west by the Mississippi River. Whiteside County comprises the Sterling, IL Micropolitan Statistical Area, which is also included in the Dixon-Sterling, IL Combined Statistical Area. U.S. President Ronald Reagan was born in 1911 in the Whiteside County community of Tampico.