Resident Population in Petroleum County, MT was 0.55400 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Petroleum County, MT reached a record high of 0.70000 in January of 1971 and a record low of 0.43300 in January of 2007. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Petroleum County, MT - last updated from the United States Federal Reserve on May of 2024.