Estimate, Median Age by Sex, Total Population (5-year estimate) in St. Croix County, WI was 39.70000 Years of Age in January of 2022, according to the United States Federal Reserve. Historically, Estimate, Median Age by Sex, Total Population (5-year estimate) in St. Croix County, WI reached a record high of 39.70000 in January of 2022 and a record low of 36.00000 in January of 2009. Trading Economics provides the current actual value, an historical data chart and related indicators for Estimate, Median Age by Sex, Total Population (5-year estimate) in St. Croix County, WI - last updated from the United States Federal Reserve on May of 2024.