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.

History Rock County was created as a territorial county on December 7, 1836, from Milwaukee County and fully organized February 19, 1839. The county is named for the Rock River, which bisects the county from north to south."Rock County, origin of place name " Dictionary of Wisconsin History.

Geography According to the U.S. Census Bureau, the county has a total area of , of which is land and (1.1%) is water.

Cook Memorial Arboretum, a natural area with birding and nature trails, is located northwest of Janesville. It is owned by the Janesville School District.Great Wisconsin Birding & Nature Trail. Cook Memorial Arboretum.

Transportation Major highways

Interstate 39 Interstate 43 Interstate 90 U.S. Highway 12 U.S. Highway 14 U.S. Highway 51 Highway 11 Highway 26 Highway 59 Highway 67 Highway 81 Highway 89 Highway 104 Highway 138 Highway 140 Highway 213

Railroads Canadian Pacific Union Pacific Wisconsin and Southern Railroad

Buses Beloit Transit Janesville Transit System

Airport Southern Wisconsin Regional Airport (KJVL) serves Rock County and the surrounding communities.

Adjacent counties Green County – west Dane County – north Jefferson County – northeast Walworth County – east Boone County, Illinois – south Winnebago County, Illinois – south

Demographics

Racial and ethnic composition +Rock County, Wisconsin – Racial and ethnic compositionRace / ethnicity (NH = Non-Hispanic)Pop 1980Pop 1990Pop 2000Pop 2010 Pop 2020% 1980% 1990% 2000% 2010% 2020White alone (NH)132,785129,788135,884135,526129,79695.24%93.03%89.22%84.53%79.30%Black or African American alone (NH)4,6606,5936,9437,7668,0603.34%4.73%4.56%4.84%4.92%Native American or Alaska Native alone (NH)2693563763833860.19%0.26%0.25%0.24%0.24%Asian alone (NH)5399321,1801,6032,0220.39%0.67%0.77%1.00%1.24%Native Hawaiian or Pacific Islander alone (NH)x included in the Asian category in the 1980 Censusx included in the Asian category in the 1990 Census503550xx0.03%0.02%0.03%Other race alone (NH)209871431255230.15%0.06%0.09%0.08%0.32%Mixed race or Multiracial (NH)x not an option in the 1980 Censusx not an option in the 1990 Census1,7782,7697,050xx1.17%1.73%4.31%Hispanic or Latino (any race)9581,7545,95312,12415,8000.69%1.26%3.91%7.56%9.65%Total139,420139,510152,307160,331163,687 100.00%100.00%100.00%100.00%100.00%

2020 census

As of the 2020 census, the population was 163,687 and the median age was 40.3 years. 22.9% of residents were under the age of 18 and 17.6% of residents were 65 years of age or older. For every 100 females there were 97.5 males, and for every 100 females age 18 and over there were 95.1 males age 18 and over.

The population density was , and there were 70,068 housing units at an average density of .

The racial makeup of the county was 81.3% White, 5.1% Black or African American, 0.5% American Indian and Alaska Native, 1.3% Asian, <0.1% Native Hawaiian and Pacific Islander, 4.6% from some other race, and 7.2% from two or more races. Hispanic or Latino residents of any race comprised 9.7% of the population.

80.0% of residents lived in urban areas, while 20.0% lived in rural areas.

There were 65,937 households in the county, of which 29.6% had children under the age of 18 living in them. Of all households, 46.1% were married-couple households, 18.6% were households with a male householder and no spouse or partner present, and 26.1% were households with a female householder and no spouse or partner present. About 28.3% of all households were made up of individuals and 12.0% had someone living alone who was 65 years of age or older.

Of those housing units, 5.9% were vacant. Among occupied housing units, 69.0% were owner-occupied and 31.0% were renter-occupied. The homeowner vacancy rate was 1.0% and the rental vacancy rate was 4.8%.

2010 census

As of the 2010 census, there were 160,331 people residing in the county.

2000 census

As of the 2000 census, there were 152,307 people, 58,617 households, and 40,387 families residing in the county. The population density was . There were 62,187 housing units at an average density of .

The racial makeup of the county was 91.01% white, 4.63% black or African American, 0.28% Native American, 0.78% Asian, 0.04% Pacific Islander, 1.77% from other races, and 1.50% from two or more races. 3.91% of the population were Hispanic or Latino of any race. 32.8% were of German, 13.0% Norwegian, 10.1% Irish, 7.5% English and 5.5% American ancestry.

There were 58,617 households, out of which 33.60% had children under the age of 18 living with them, 53.50% were married couples living together, 10.90% had a female householder with no husband present, and 31.10% were non-families. 25.10% of all households were made up of individuals, and 9.70% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 3.03.

In the county, the population was spread out, with 26.50% under the age of 18, 8.60% from 18 to 24, 29.80% from 25 to 44, 22.30% from 45 to 64, and 12.70% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 97.00 males. For every 100 females age 18 and over, there were 94.10 males.

Communities

Cities Beloit Brodhead (mostly in Green County) Edgerton (partly in Dane County) Evansville Janesville (County seat) Milton

Villages Clinton Orfordville Footville

Towns

Avon Beloit Bradford Center Clinton Fulton Harmony Janesville Johnstown La Prairie Lima Magnolia Milton Newark Plymouth Porter Rock Spring Valley Turtle Union

Census-designated places Fulton Hanover Shopiere

Unincorporated communities

Afton Anderson Avalon Avon Belcrest Bergen Cainville Center Charlie Bluff Cooksville Coopers Shores Crestview Emerald Grove Fairfield (partial) Foxhollow Indianford Johnstown Johnstown Center Koshkonong (partial) Leyden Lima Center Magnolia Mallwood Maple Beach Newark Newville Porters Stebbinsville Tiffany Union Victory Heights

Ghost towns/neighborhoods Fellows Jefferson Prairie Settlement

Politics

Since 1988, Rock County has consistently voted for the Democratic candidate in every Presidential election. In 2024, Kamala Harris carried the county by the smallest margin of victory since Michael Dukakis in 1988.

Education School districts include: - Text list

Albany School District School District of Beloit Beloit Turner School District Brodhead School District Clinton Community School District Delavan-Darien School District Edgerton School District Evansville Community School District Fort Atkinson School District School District of Janesville Milton School District Oregon School District Parkview School District Stoughton Area School District Whitewater School District

There is a state-operated school, Wisconsin School for the Blind and Visually Impaired.

See also National Register of Historic Places listings in Rock County, Wisconsin

References

Further reading Brown, William F. Rock County, Wisconsin: A New History... Vol. 1, Chicago: Cooper, 1908. Brown, William F. Rock County, Wisconsin: A New History... Vol. 2, Chicago: Cooper, 1908. Commemorative Biographical Record of the Counties of Rock, Green, Grant, Iowa, and Lafayette, Wisconsin, Containing Biographical Sketches of Prominent and Representative Citizens, and of Many of the Early Settled Families. Chicago: J. H. Beers and Co., 1901. The History of Rock County, Wisconsin. Chicago: Western Historical Company, 1879. Portrait and Biographical Album of Rock County, Wisconsin. Chicago: Acme Publishing Company, 1889. Sayre, David F. "Early Life in Southern Wisconsin", Wisconsin Magazine of History, vol. 3, no. 4 (June 1920), pp. 420–427. Smith, Isaac T. "Early Settlement of Rock County" in Wisconsin Historical Collections, vol. VI. Madison, Wis.: Atwood & Culver, 1872, pp. 416–425. Walterman, Thomas. There Stands "Old Rock": Rock County, Wisconsin and the War to Preserve the Union. Friendship, Wis.: New Past Press, 2001.

External links Rock County government website Rock County map from the Wisconsin Department of Transportation Rock County 5.0 Rock County Historical Society Rock County Genealogical Society Beloit Janesville Symphony