COUNTY · WI
St. Croix County, Wisconsin
St. Croix County is a county in Wisconsin with FIPS code 55109 and an estimated population of 96,763 (Census 2023), 17th largest of 72 in the state.
County facts
- Name
- St. Croix County
- State
- Wisconsin
- Type
- county
- FIPS code
- 55109
- State FIPS
- 55
- Population (2023)
- 96,763
- Change since 2020
- +3.1%
- State rank
- 17 of 72
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for St. Croix County?
St. Croix County, Wisconsin has the five-digit FIPS code 55109: 55 for the state and 109 for the county.
What state is St. Croix County in?
St. Croix 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.