Resident Population in Yellowstone County, MT was 170.84300 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Yellowstone County, MT reached a record high of 170.84300 in January of 2023 and a record low of 87.36700 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Yellowstone County, MT - last updated from the United States Federal Reserve on May of 2024.