Resident Population in Washington County, CO was 4.85500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Washington County, CO reached a record high of 5.55000 in January of 1970 and a record low of 4.43000 in January of 2009. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Washington County, CO - last updated from the United States Federal Reserve on May of 2024.