Jo Daviess County is the northwesternmost county in the U.S. state of Illinois. According to the 2020 census, it had a population of 22,035. Its county seat is Galena. Jo Daviess County is part of the Tri-State Area and is located near Dubuque, Iowa and Platteville, Wisconsin. As part of the Driftless Area, Jo Daviess County is known for its scenic stretches of road, high hills and valley views.