Rock County Demographics

A map of Rock County's Population by Race

Race	2024 Pop	2020 Pop	2024 %	2020 %
White	130,867	129,796	79.6%	79.3%
Hispanic	16,646	15,800	10.1%	9.7%
Black	7,584	8,060	4.6%	4.9%
Multiracial	6,925	7,050	4.2%	4.3%
Asian	1,779	2,022	1.1%	1.2%
Native American/Other	549	959	0.3%	0.6%

Rock County, Wisconsin has an estimated population of 164,350, a less than 1% change from the 163,687 recorded in the 2020 Census. The population is 79.6% White, 10.1% Hispanic, 4.6% Black, 4.2% Multiracial, 1.1% Asian, and 0.3% Native American/Other. This demographic dot map shows the population of Rock County, with one dot drawn for each person counted by the Census, color-coded by race.

Rock has become slightly less racially diverse since the 2020 Census. It is less diverse than Wisconsin overall. Demographers use a diversity index to measure the probability that two randomly selected individuals belong to different racial or ethnic groups. In Rock County, that probability was 35.7% in 2020 and 35.2% in the most recent ACS estimates.

Rock County is ranked the 9th most populous county in Wisconsin, out of 72 counties. Rock County was ranked the 9th most populous county in the 2020 Census.

Rock County's White Population

130,867 residents of Rock County, or 79.6% of the population, identify as White. The share of White residents in Rock County is comparable to the share in Wisconsin overall, where 78.6% of the population is White. Rock County ranks 64th statewide in terms of White residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's White population has remained roughly the same. White residents' share of Rock County's population has remained roughly unchanged at 79.6%.

Rock County is more White than neighboring Winnebago County (63.8% White), Boone County (68% White), and Dane County (75.8% White). Rock County is less White than neighboring Jefferson County (87% White), and Walworth County (83.1% White).

Rock County's Black Population

7,584 residents of Rock County, or 4.6% of the population, identify as Black. The share of Black residents in Rock County is comparable to the share in Wisconsin overall, where 5.9% of the population is Black. Rock County ranks 5th statewide in terms of Black residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's Black population has declined by an estimated 5.9%. Black residents' share of Rock County's population has remained roughly unchanged at 4.6%.

Rock County is more Black than neighboring Boone County (2.3% Black), Jefferson County (0.9% Black), and Walworth County (0.7% Black). Rock County is less Black than neighboring Winnebago County (11.6% Black), and Dane County (5.1% Black).

Rock County's Asian Population

1,779 residents of Rock County, or 1.1% of the population, identify as Asian. The share of Asian residents in Rock County is comparable to the share in Wisconsin overall, where 2.9% of the population is Asian. Rock County ranks 20th statewide in terms of Asian residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's Asian population has declined by an estimated 12.0%. Asian residents' share of Rock County's population has remained roughly unchanged at 1.1%.

Rock County is more Asian than neighboring Boone County (1% Asian), Jefferson County (0.6% Asian), and Walworth County (0.8% Asian). Rock County is less Asian than neighboring Winnebago County (2.9% Asian), and Dane County (6.1% Asian).

Rock County's Hispanic Population

16,646 residents of Rock County, or 10.1% of the population, identify as Hispanic. The share of Hispanic residents in Rock County is slightly higher than in Wisconsin overall, where 8% of the population is Hispanic. Rock County ranks 7th statewide in terms of Hispanic residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's Hispanic population has grown by an estimated 5.4%. Hispanic residents' share of Rock County's population has remained roughly unchanged at 10.1%.

Rock County is more Hispanic than neighboring Jefferson County (8.5% Hispanic), and Dane County (7.8% Hispanic). Rock County is less Hispanic than neighboring Winnebago County (15.5% Hispanic), Boone County (25.6% Hispanic), and Walworth County (12.1% Hispanic).

Rock County's Native American/Other Population

549 residents of Rock County, or 0.3% of the population, identify as American Indian/Alaska Native/Native Hawaiian/Pacific Islander/Other. The share of Native American/Other residents in Rock County is comparable to the share in Wisconsin overall, where 0.9% of the population is Native American/Other. Rock County ranks 48th statewide in terms of Native American/Other residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's Native American/Other population has declined by an estimated 42.8%. Native American/Other residents' share of Rock County's population has remained roughly unchanged at 0.3%.

Rock County is less Native American/Other than neighboring Winnebago County (0.5% Native American/Other), Boone County (0.4% Native American/Other), Dane County (0.6% Native American/Other), and Walworth County (0.4% Native American/Other).

Rock County's Multiracial Population

6,925 residents of Rock County, or 4.2% of the population, identify as Multiracial. The share of Multiracial residents in Rock County is comparable to the share in Wisconsin overall, where 3.7% of the population is Multiracial. Rock County ranks 8th statewide in terms of Multiracial residents as a share of the population, out of 72 counties.

Since the 2020 Census, Rock County's Multiracial population has declined by an estimated 1.8%. Multiracial residents' share of Rock County's population has remained roughly unchanged at 4.2%.

Rock County is more Multiracial than neighboring Boone County (2.8% Multiracial), Jefferson County (2.7% Multiracial), and Walworth County (2.8% Multiracial). Rock County is less Multiracial than neighboring Winnebago County (5.8% Multiracial), and Dane County (4.6% Multiracial).

Sources: Most recent population estimates are from the 2020-2024 American Community Survey 5-Year Estimates. 2020 population counts and map data are from 2020 Census State Redistricting Data. Geographic data are from Census TIGER/Line Shapefiles.