How many people live in Rock County, WI?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 165,500 people living in Rock County, WI. That makes Rock County the ninth-most populous county in Wisconsin. It is home to 2.8% of people living in the state.
165K
population of Rock County, WI (2024)
2.8%
County share of the Wisconsin population (2024)
About 165,500 people lived in Rock County, WI in 2024.
Population estimates, 2000–2024
What are Rock County, WI’s age demographics?
About 31,200 Rock County, WI residents are aged 65 and older in 2024. That represents 18.8% of its population. For comparison, the age group represents 19.6% of Wisconsin’s population and 18% in the US overall.
Another 36,000 Rock County residents, or 21.8% of the population, were children under 18. For comparison, the age group represents 20.8% of Wisconsin’s population and 21.6% in the US overall.
A lower share of Rock County, WI's population is aged 25–44 than the US as a whole.
Population estimates by age group, (2024)
What are Rock County, WI’s racial and ethnic demographics?
Non-Hispanic white residents make up 80.2% of the Rock County, WI population, higher than the national share of 57.5%. Rock County, WI also has a larger share of people identifying as non-Hispanic two or more races (2.6%) than the US overall (2.5%).
In contrast, Rock County’s Hispanic population accounts for 10.7%, below the 20% nationwide, and the non-Hispanic Black or African American population makes up 4.9% of the county, compared with 12.6% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
Rock County, WI has a higher share of a Hispanic population than Wisconsin as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in Rock County, WI is Janesville with about 66,400 residents in 2024.
Cities and towns in Rock County, WI ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Janesville | 66,428 |
| 2. | Beloit | 36,633 |
| 3. | Beloit | 7,904 |
| 4. | Edgerton (pt.) | 5,991 |
| 5. | Evansville | 5,819 |
| 6. | Milton | 5,778 |
| 7. | Janesville | 3,692 |
| 8. | Fulton | 3,667 |
| 9. | Milton | 3,122 |
| 10. | Rock | 3,037 |
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Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
