Estimate, Median Age by Sex, Total Population (5-year estimate) in Mercer County, MO was 41.70000 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 Mercer County, MO reached a record high of 45.40000 in January of 2009 and a record low of 41.20000 in January of 2021. 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 Mercer County, MO - last updated from the United States Federal Reserve on May of 2024.