Rock County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 163,687. Its county seat is Janesville. Rock County comprises the Janesville-Beloit, WI Metropolitan Statistical Area and is included in the Madison-Janesville-Beloit, WI Combined Statistical Area.
Rock County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 163,687. Its county s!eat is Janesville. Rock County comprises the Janesville-Beloit, WI Metr:opolitan Statistical Area and is included in the Madison-Janesville-Beloit, WI Combined Statistical, Area