COUNTY · WI
Rock County, Wisconsin
Rock County is a county in Wisconsin with FIPS code 55105 and an estimated population of 164,278 (Census 2023), 9th largest of 72 in the state.
County facts
- Name
- Rock County
- State
- Wisconsin
- Type
- county
- FIPS code
- 55105
- State FIPS
- 55
- Population (2023)
- 164,278
- Change since 2020
- +0.3%
- State rank
- 9 of 72
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Rock County?
Rock County, Wisconsin has the five-digit FIPS code 55105: 55 for the state and 105 for the county.
What state is Rock County in?
Rock County is in Wisconsin.
How do I know if an address is in this county?
Use the address lookup. ZIP codes and city names can cross county lines, so an address is the reliable check.
Sources: U.S. Census Bureau geographic reference files; Census Bureau Population Estimates, Vintage 2023. Last reviewed 2026-10-27.