Rock County, Wisconsin | |
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.jpg) Rock County Courthouse | |
 Seal | |
 Location within the U.S. state ofWisconsin | |
| Coordinates:42°40′N89°04′W / 42.67°N 89.07°W /42.67; -89.07 | |
| 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 | |
• Total | 163,687 |
• Estimate (2024) | 165,461 |
| • Density | 228/sq mi (88.0/km2) |
| Time zone | UTC−6 (Central) |
| • Summer (DST) | UTC−5 (CDT) |
| Congressional districts | 1st,2nd |
| Website | www |
Rock County is acounty in theU.S. state ofWisconsin. As of the2020 census, the population was 163,687.[1] Itscounty seat isJanesville.[2] Rock County comprises the Janesville–Beloitmetropolitan statistical area and is included in theMadison–Janesville–Beloit combined statistical area.
Rock County was created as a territorial county on December 7, 1836, fromMilwaukee County and fully organized February 19, 1839.[3] The county is named for theRock River, which bisects the county from north to south.[4]
According to theU.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 theJanesville School District.[6]
Southern Wisconsin Regional Airport (KJVL) serves Rock County and the surrounding communities.
| 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% | |
| 2024 (est.) | 165,461 | [7] | 1.1% |
| U.S. Decennial Census[8] 1790–1960[9] 1900–1990[10] 1990–2000[11] 2010[12] 2020[1] | |||
As of the2020 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.[1][13]
The population density was 227.9 people per square mile (88.0 people/km2), and there were 70,068 housing units at an average density of 97.6 units per square mile (37.7 units/km2).[1][13]
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 andPacific Islander, 4.6% from some other race, and 7.2% fromtwo or more races.Hispanic or Latino residents of any race comprised 9.7% of the population.[14]
80.0% of residents lived in urban areas, while 20.0% lived in rural areas.[15]
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.[13]
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%.[13]
As of the2010 census, there were 160,331 people residing in the county.[16]
As of the2000 census, there were 152,307 people, 58,617 households, and 40,387 families residing in the county. Thepopulation 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).[16]
The racial makeup of the county was 91.01%white, 4.63%black orAfrican American, 0.28%Native American, 0.78%Asian, 0.04%Pacific Islander, 1.77% fromother races, and 1.50% from two or more races. 3.91% of the population wereHispanic orLatino of any race. 32.8% were ofGerman, 13.0%Norwegian, 10.1%Irish, 7.5%English and 5.5%American ancestry.[16]
There were 58,617 households, out of which 33.60% had children under the age of 18 living with them, 53.50% weremarried 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.[16]
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.[16]
| Year | Republican | Democratic | Third party(ies) | |||
|---|---|---|---|---|---|---|
| No. | % | No. | % | No. | % | |
| 1892 | 6,052 | 55.24% | 4,231 | 38.62% | 673 | 6.14% |
| 1896 | 8,282 | 67.46% | 3,655 | 29.77% | 340 | 2.77% |
| 1900 | 8,249 | 69.97% | 3,094 | 26.24% | 447 | 3.79% |
| 1904 | 7,972 | 71.65% | 2,348 | 21.10% | 807 | 7.25% |
| 1908 | 7,839 | 66.81% | 3,227 | 27.50% | 668 | 5.69% |
| 1912 | 4,276 | 43.21% | 3,032 | 30.64% | 2,587 | 26.14% |
| 1916 | 7,011 | 61.09% | 4,015 | 34.98% | 451 | 3.93% |
| 1920 | 16,152 | 83.53% | 2,447 | 12.65% | 738 | 3.82% |
| 1924 | 14,815 | 60.92% | 1,453 | 5.97% | 8,052 | 33.11% |
| 1928 | 21,497 | 70.75% | 8,726 | 28.72% | 161 | 0.53% |
| 1932 | 16,825 | 56.07% | 12,612 | 42.03% | 571 | 1.90% |
| 1936 | 14,693 | 43.56% | 17,991 | 53.34% | 1,045 | 3.10% |
| 1940 | 20,141 | 53.15% | 17,543 | 46.29% | 214 | 0.56% |
| 1944 | 18,477 | 52.23% | 16,766 | 47.39% | 133 | 0.38% |
| 1948 | 17,068 | 50.66% | 16,150 | 47.93% | 474 | 1.41% |
| 1952 | 27,837 | 64.64% | 15,183 | 35.26% | 45 | 0.10% |
| 1956 | 28,980 | 67.42% | 13,834 | 32.18% | 173 | 0.40% |
| 1960 | 29,675 | 60.63% | 19,194 | 39.22% | 76 | 0.16% |
| 1964 | 20,372 | 41.85% | 28,257 | 58.04% | 55 | 0.11% |
| 1968 | 25,229 | 50.97% | 20,567 | 41.56% | 3,697 | 7.47% |
| 1972 | 30,361 | 58.03% | 21,033 | 40.20% | 925 | 1.77% |
| 1976 | 28,325 | 49.04% | 28,048 | 48.56% | 1,389 | 2.40% |
| 1980 | 30,960 | 50.60% | 24,740 | 40.44% | 5,482 | 8.96% |
| 1984 | 32,491 | 54.76% | 26,433 | 44.55% | 410 | 0.69% |
| 1988 | 28,178 | 48.43% | 29,576 | 50.83% | 434 | 0.75% |
| 1992 | 21,942 | 31.79% | 31,154 | 45.13% | 15,929 | 23.08% |
| 1996 | 20,096 | 33.32% | 32,450 | 53.80% | 7,774 | 12.89% |
| 2000 | 27,467 | 39.01% | 40,472 | 57.49% | 2,465 | 3.50% |
| 2004 | 33,151 | 41.19% | 46,598 | 57.90% | 730 | 0.91% |
| 2008 | 27,364 | 34.56% | 50,529 | 63.82% | 1,276 | 1.61% |
| 2012 | 30,517 | 37.82% | 49,219 | 61.00% | 954 | 1.18% |
| 2016 | 31,493 | 41.40% | 39,339 | 51.71% | 5,242 | 6.89% |
| 2020 | 37,138 | 43.51% | 46,658 | 54.66% | 1,564 | 1.83% |
| 2024 | 40,218 | 45.54% | 46,642 | 52.82% | 1,450 | 1.64% |
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 sinceMichael Dukakis in 1988.
School districts include:[18]
There is a state-operated school,Wisconsin School for the Blind and Visually Impaired.
Places adjacent to Rock County, Wisconsin | |
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Municipalities and communities ofRock County, Wisconsin,United States | ||
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| Cities |  | |
| Villages | ||
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| Other communities | ||
| Former communities | ||
| Footnotes | ‡This populated place also has portions in an adjacent county or counties | |
| International | |
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| National | |
| Other | |
