Resident Population in Marion County, OR was 346.74100 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Marion County, OR reached a record high of 347.77500 in January of 2021 and a record low of 151.30900 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Marion County, OR - last updated from the United States Federal Reserve on May of 2024.