Resident Population in Contra Costa County, CA was 1155.02500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Contra Costa County, CA reached a record high of 1165.98600 in January of 2020 and a record low of 556.11600 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Contra Costa County, CA - last updated from the United States Federal Reserve on May of 2024.