• county
  • FIPS 55105
  • Largest town: Janesville

Rock County, Wisconsin

Rock County had 165,461 residents in the Census Vintage 2024 estimate, on 718.2 square miles of land. It ranks 9th of 72 in Wisconsin by population and 41st by land area.

Population
165,461
#9 of 72 in Wisconsin · #425 in US
Area
718.2 sq mi
#41 of 72 in Wisconsin · #1,251 in US
Density
230 / sq mi
#13 of 72 in Wisconsin · #523 in US
Median household income
$73,656
#25 of 72 in Wisconsin · #750 in US

Census Vintage 2024 estimates · SAIPE 2023 income · 2024 Gazetteer land area

Rock County within Wisconsin. Pin: Madison.

Measure from here

Tools and pages that start from Rock County

Rock County population, land area and income

Rock County had 165,461 residents in the Census Vintage 2024 estimate, on 718.2 square miles of land. It ranks 9th of 72 in Wisconsin by population and 41st by land area. That works out to 230.4 people per square mile, 2.4 times the US average of 96.3, and in the top quarter nationally.

The median county-equivalent in Wisconsin has 41,821 residents, so Rock County is 4.0 times that size.

Its SAIPE 2023 median household income of $73,656 is in the top quarter among 3,143 counties with an estimate.

National rank among 3,144

Population

165,461

3144th1st

425th of 3,144 (US)

Land area

718 sq mi

3144th1st

1251st of 3,144 (US)

Density

230.4 / sq mi

3144th1st

523rd of 3,144 (US)

Median household income

$73,656

3143rd1st

750th of 3,143 (US)

Rank within Wisconsin (72)

Population

165,461

72nd1st

9th of 72 (WI)

Land area

718 sq mi

72nd1st

41st of 72 (WI)

Density

230.4 / sq mi

72nd1st

13th of 72 (WI)

Median household income

$73,656

72nd1st

25th of 72 (WI)

How Rock County's population changed since 2020

Rock County gained 1,700 residents between the July 2020 and July 2024 estimates, a rise of 1.0%. That ranks 38th of 72 in Wisconsin for growth. The median Wisconsin county changed by +1.0%, and the state as a whole by +1.1%.

Since the April 2020 estimates base, Rock County recorded 7,621 births and 7,813 deaths, a natural change of -192. Net international migration added +657 and net domestic migration, people moving to or from other US counties, came to +1,266. The largest single component was domestic migration, which added 1,266 people.

163.8k2020164.1k2021164.0k2022164.4k2023165.5k2024
Census Vintage 2024 county estimates for July 1 of each year. The axis starts above zero so year-to-year changes are visible.

Components of change, April 2020 to July 2024

Births
7,621
Deaths
7,813
Net international migration
+657
Net domestic migration
+1,266
Change, July 2023 to July 2024
+1,018

Where Rock County is

The Census internal point of Rock County is at 42.669900, -89.075300. It sits in UTM zone 16N. The map shades Wisconsin's 72 county-equivalents by population change from 2020 to 2024, darker for faster growth, with Rock County outlined. Dots are towns of 1,000+ people with residents in it.

Barron County: +0.2%Green County: +0.4%Dunn County: +1.5%Jefferson County: +0.0%Lincoln County: +0.1%Rusk County: -0.1%Fond du Lac County: +0.1%Marquette County: +1.0%Outagamie County: +2.3%Waupaca County: -1.2%Oneida County: +0.8%Eau Claire County: +2.8%Washington County: +1.4%Portage County: +2.3%Menominee County: +0.7%Clark County: +0.5%Monroe County: +0.2%Milwaukee County: -1.5%Buffalo County: +1.1%Lafayette County: +4.2%Ozaukee County: +2.5%Rock County: +1.0%Sheboygan County: +0.2%Green Lake County: +1.8%Waukesha County: +2.3%Calumet County: +2.1%Dodge County: -0.8%Wood County: -0.3%Winnebago County: +0.9%Sawyer County: +4.0%Dane County: +4.6%Sauk County: +1.1%Pepin County: +2.9%Adams County: +3.2%Price County: +0.4%Taylor County: +1.1%Grant County: +0.7%Trempealeau County: -0.0%Vernon County: +2.1%Waushara County: +2.2%Iowa County: +1.0%Crawford County: -0.5%Kenosha County: -0.3%Shawano County: +1.1%Juneau County: -0.7%Jackson County: -0.3%Vilas County: +3.7%Bayfield County: +3.7%Chippewa County: +1.5%Iron County: +1.5%Racine County: +0.3%Door County: +1.3%Ashland County: +1.1%Kewaunee County: +0.9%Polk County: +1.8%Florence County: +2.4%Douglas County: -0.2%Forest County: +3.7%Columbia County: -0.7%Walworth County: +0.7%La Crosse County: +0.1%Manitowoc County: +0.1%Oconto County: +2.5%Langlade County: +0.4%Marathon County: +0.7%Washburn County: +2.2%Brown County: +1.8%Richland County: -0.9%Marinette County: +1.1%St. Croix County: +4.3%Pierce County: +2.7%Burnett County: +3.7%
Change 2020 to 2024
  1. < +0.1%
  2. < +0.7%
  3. < +1.3%
  4. < +2.3%
  5. ≥ +2.3%
no data

Orange pin: Rock County internal point. Dark pin: Madison.

Internal point

Decimal
42.669900, -89.075300
DMS
42°40'11.64"N 89°04'31.08"W
UTM
16N 329939.9E 4726246.7N
Geohash
dp8dtpc65
Plus code
86JGMW9F+XV

Towns in Rock County

8 incorporated places of 1,000+ people have residents in Rock County, 124,636 people together, or 75% of the county. Each figure counts only the part of the town inside Rock County; towns marked "part" extend into another county. The largest is Janesville with 66,428.

  1. 01Janesville66,428
  2. 02Beloit36,633
  3. 03Edgerton (part)5,991
  4. 04Evansville5,819
  5. 05Milton5,778
  6. 06Clinton2,302
  7. 07Orfordville1,598
  8. 08Brodhead (part)87
Census Vintage 2024 subcounty estimates, county parts of incorporated places (SUMLEV 157).

Counties bordering Rock County

The Census 2024 county adjacency file lists 6 neighbors for Rock County, including 2 across a state line. The most populous is Dane County, WI, with 588,347 residents. Distances run between Census internal points in a straight line.

Distance to Madison and the nearest big city

Madison is 32.1 miles NNW of Rock County's internal point in a straight line. The nearest place of 100,000 or more is Rockford, IL (population 147,486), 28.4 miles away. The nearest place of 10,000 or more is Janesville, WI (population 66,428), 3.3 miles away.

Rock County FIPS code

The FIPS code of Rock County is 55105: state code 55 for Wisconsin plus county code 105. Use it as text, with the leading zero, when joining Census, BLS, or CDC county tables. SAIPE lists its 2023 median household income as $73,656.

Questions people ask

What is the population of Rock County, Wisconsin?

The Census Vintage 2024 estimate for July 1, 2024 is 165,461. That is up 1,700 people (1.0%) from the July 2020 estimate of 163,761.

What is the FIPS code of Rock County?

55105. The first two digits (55) are Wisconsin; the last three (105) identify the county.

What is the largest town in Rock County?

Janesville, with 66,428 residents inside Rock County in 2024.

Which counties border Rock County?

6 county-equivalents border it in the Census 2024 adjacency file: Dane County, WI; Winnebago County, IL; Walworth County, WI; Jefferson County, WI; Boone County, IL; Green County, WI.

Sources and data as of

Data as of: Census Vintage 2024 population estimates, 2024 Gazetteer land area and internal points, SAIPE 2023 median household income.

  1. 01Census Vintage 2024 county population estimates
  2. 02Census 2024 Gazetteer, counties
  3. 03Census SAIPE 2023 state and county estimates
  4. 04Census Vintage 2024 subcounty population estimates
  5. 05Census 2024 county adjacency file
  6. 06Census 2024 cartographic boundary file, counties (1:5,000,000)

How every number is computed: methodology. Spotted a wrong figure? Report an error.