Rock County, Wisconsin

Rock County
Rock County Courthouse
Location within the U.S. state of Wisconsin
Wisconsin's location within the U.S.
Coordinates: 42°40′N 89°04′W / 42.67°N 89.07°W / 42.67; -89.07
Country United States
State Wisconsin
Founded1839
Named afterRock River
SeatJanesville
Largest cityJanesville
Area
  Total
726 sq mi (1,880 km2)
  Land718 sq mi (1,860 km2)
  Water8.0 sq mi (21 km2)  1.1%
Population
 (2020)
  Total
163,687
  Estimate 
(2023)
164,278
  Density230/sq mi (87/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional districts1st, 2nd
Websitewww.co.rock.wi.us

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.