Estimate, Median Age by Sex, Total Population (5-year estimate) in King County, WA was 37.20000 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 King County, WA reached a record high of 37.20000 in January of 2014 and a record low of 36.80000 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 King County, WA - last updated from the United States Federal Reserve on May of 2024.