Rock County is a county in the U.S. state of Wisconsin. As of the 2010 census, the population was 160,331. 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.
History
Rock County was created in 1836 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.
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.
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 140
Highway 213
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
As of the census of 2010, there were 160,331 people, 58,617 households, and 40,387 families residing in the county. The population density was 211 people per square mile (82/km2). There were 62,187 housing units at an average density of 86 per square mile (33/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
Milton
Villages
Clinton
Orfordville
Footville
Towns
Avon
Beloit
Bradford
Center
Clinton
Edgerton
Fulton
Harmony
Janesville
Johnstown
La Prairie
Lima
Magnolia
Milton
Newark
Plymouth
Porter
Rock
Spring Valley
Turtle
Union
Census-designated place
Hanover
Unincorporated communities
Afton
Anderson
Avon
Avalon
Belcrest
Bergen
Cainville
Center
Charlie Bluff
Cooksville
Coopers Shores
Crestview
Emerald Grove
Fairfield (partial)
Foxhollow
Fulton
Indianford
Johnstown
Johnstown Center
Koshkonong (partial)
Leyden
Lima Center
Magnolia
Maple Beach
Newark
Newville
Porters
Shopiere
Stebbinsville
Tiffany
Union
Victory Heights
Ghost towns/neighborhoods
Fellows
Jefferson Prairie Settlement
Politics
Hillary Clinton carried the county in 2016, but it was the smallest margin of victory since Michael Dukakis in 1988.
Tree cities
Beloit
Clinton
Edgerton
Evansville
Janesville
