Rock County, Wisconsin

Rock County, Wisconsin
Rock County Courthouse
Location within the U.S. state of Wisconsin
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 
(2024)
165,461
 • Density228/sq mi (88.0/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 metropolitan statistical area and is included in the Madison–Janesville–Beloit combined statistical area.