Rockford is the third largest city in the U.S. state of Illinois, the 171st most populous city in the United States, the largest city in Illinois outside the Chicago metropolitan area, and the city of the 148th most populous metropolitan area in the United States. It is the county seat of Winnebago County and is on both banks of the Rock River in far northern Illinois. A small portion of Rockford dips down into neighboring Ogle County. According to 2010 census data, the City of Rockford had a population of 152,871, with an outlying metropolitan area population of 348,360, which was estimated to have decreased to 150,251 and 344,623, respectively, by July 2013. During 2017, a special census was completed putting the population at 153,379.
Settled in the mid-1830s, the position of the city on the Rock River made its location strategic for industrial development. In the second half of the 19th century, Rockford was notable for its output of heavy machinery and tools; by the twentieth century, it was the second leading center of furniture manufacturing in the nation, and 94th largest city. During the second half of the 20th century, Rockford struggled alongside many Rust Belt cities.