Rockford is the third largest city in the U.S. state of Illinois, the 160th most populous city in the United States, and the 112th 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. Wikipedia

Springfield is the capital of the US state of Illinois and the county seat of Sangamon County with a population of 116,250, making it the sixth most populated city in the state. It is the largest city in central Illinois. Wikipedia