Estimate, Median Age by Sex, Total Population (5-year estimate) in Jefferson County, CO was 40.20000 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 Jefferson County, CO reached a record high of 40.50000 in January of 2016 and a record low of 39.50000 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 Jefferson County, CO - last updated from the United States Federal Reserve on May of 2024.