Rock County, Wisconsin

Rock County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 163,687.^[1] Its county seat is Janesville.^[2] Rock County comprises the Janesville-Beloit, WI Metropolitan Statistical Area and is included in the Madison-Janesville-Beloit, WI Combined Statistical Area.

Rock County
County
Rock County Courthouse
Seal
Location within the U.S. state of Wisconsin
Wisconsin's location within the U.S.
Coordinates: 42°40′N 89°04′W
Country	United States
State	Wisconsin
Founded	1839
Named after	Rock River
Seat	Janesville
Largest city	Janesville
Area
• Total	726 sq mi (1,880 km2)
• Land	718 sq mi (1,860 km2)
• Water	8.0 sq mi (21 km2)  1.1%
Population  (2020)[1]
• Total	163,687
• Estimate  (2023)	164,278
• Density	230/sq mi (87/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional districts	1st, 2nd
Website	www.co.rock.wi.us

History

Rock County was created as a territorial county on December 7, 1836, from Milwaukee County and fully organized February 19, 1839.^[3] The county is named for the Rock River, which bisects the county from north to south.^[4]

Geography

According to the U.S. Census Bureau, the county has a total area of 726 square miles (1,880 km²), of which 718 square miles (1,860 km²) is land and 8.0 square miles (21 km²) (1.1%) is water.^[5]

Cook Memorial Arboretum, a natural area with birding and nature trails, is located northwest of Janesville. It is owned by the Janesville School District.^[6]

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

Historical population

Census	Pop.	Note	%±
1840	1,701		—
1850	20,750		1,119.9%
1860	36,690		76.8%
1870	39,030		6.4%
1880	38,823		−0.5%
1890	43,220		11.3%
1900	51,203		18.5%
1910	55,538		8.5%
1920	66,150		19.1%
1930	74,206		12.2%
1940	80,173		8.0%
1950	92,778		15.7%
1960	113,913		22.8%
1970	131,970		15.9%
1980	139,420		5.6%
1990	139,510		0.1%
2000	152,307		9.2%
2010	160,331		5.3%
2020	163,687		2.1%
U.S. Decennial Census[7] 1790–1960[8] 1900–1990[9] 1990–2000[10] 2010[11] 2020[1]

As of the census of 2020,^[1] the population was 163,687. The population density was 227.9 people per square mile (88.0 people/km²). There were 70,068 housing units at an average density of 97.6 units per square mile (37.7 units/km²). The racial makeup of the county was 81.3% White, 5.1% Black or African American, 1.3% Asian, 0.5% Native American, 4.6% from other races, and 7.2% from two or more races. Ethnically, the population was 9.7% Hispanic or Latino of any race.

2000 Census Age Pyramid for Rock County

As of the census^[12] of 2010, there were 160,331 people residing in the county.

As of the census^[12] of 2000, were 152,307 people, 58,617 households, and 40,387 families residing in the county. The population density was 211 people per square mile (81 people/km²). there were 62,187 housing units at an average density of 86 units per square mile (33 units/km²). 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

United States presidential election results for Rock County, Wisconsin^[13]

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	40,218	45.54%	46,642	52.82%	1,450	1.64%
2020	37,138	43.51%	46,658	54.66%	1,564	1.83%
2016	31,493	41.40%	39,339	51.71%	5,242	6.89%
2012	30,517	37.82%	49,219	61.00%	954	1.18%
2008	27,364	34.56%	50,529	63.82%	1,276	1.61%
2004	33,151	41.19%	46,598	57.90%	730	0.91%
2000	27,467	39.01%	40,472	57.49%	2,465	3.50%
1996	20,096	33.32%	32,450	53.80%	7,774	12.89%
1992	21,942	31.79%	31,154	45.13%	15,929	23.08%
1988	28,178	48.43%	29,576	50.83%	434	0.75%
1984	32,491	54.76%	26,433	44.55%	410	0.69%
1980	30,960	50.60%	24,740	40.44%	5,482	8.96%
1976	28,325	49.04%	28,048	48.56%	1,389	2.40%
1972	30,361	58.03%	21,033	40.20%	925	1.77%
1968	25,229	50.97%	20,567	41.56%	3,697	7.47%
1964	20,372	41.85%	28,257	58.04%	55	0.11%
1960	29,675	60.63%	19,194	39.22%	76	0.16%
1956	28,980	67.42%	13,834	32.18%	173	0.40%
1952	27,837	64.64%	15,183	35.26%	45	0.10%
1948	17,068	50.66%	16,150	47.93%	474	1.41%
1944	18,477	52.23%	16,766	47.39%	133	0.38%
1940	20,141	53.15%	17,543	46.29%	214	0.56%
1936	14,693	43.56%	17,991	53.34%	1,045	3.10%
1932	16,825	56.07%	12,612	42.03%	571	1.90%
1928	21,497	70.75%	8,726	28.72%	161	0.53%
1924	14,815	60.92%	1,453	5.97%	8,052	33.11%
1920	16,152	83.53%	2,447	12.65%	738	3.82%
1916	7,011	61.09%	4,015	34.98%	451	3.93%
1912	4,276	43.21%	3,032	30.64%	2,587	26.14%
1908	7,839	66.81%	3,227	27.50%	668	5.69%
1904	7,972	71.65%	2,348	21.10%	807	7.25%
1900	8,249	69.97%	3,094	26.24%	447	3.79%
1896	8,282	67.46%	3,655	29.77%	340	2.77%
1892	6,052	55.24%	4,231	38.62%	673	6.14%

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:^[14]

• Albany School District
• Beloit School District
• 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
• Janesville School District
• 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