The largest city in this region, located near the eastern edge, is Rockford. Rockford's Metropolitan Area includes Winnebago County and Boone County (to the east), with an estimated 2009 population of 353,722.[1]
The geography of northwestern Illinois varies from that of the rest of the state. The area is primarily in the Driftless Area, which is characterized by bluffs, valleys, and rolling hills. Two counties most characteristic of the Driftless Area are Jo Daviess County and Carroll.