Resident Population in Gilliam County, OR was 2.02600 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Gilliam County, OR reached a record high of 2.34200 in January of 1970 and a record low of 1.63700 in January of 2009. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Gilliam County, OR - last updated from the United States Federal Reserve on May of 2024.