Rockford is the third largest city in the
U.S. state of
Illinois, the
171st most populous city in the
United States, and the
148th most populous region in the United States. It is the county seat of
Winnebago County and is located on both banks of the
Rock River in far
northern Illinois. 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.