Resident Population in Custer County, MT was 11.98500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Custer County, MT reached a record high of 13.24200 in January of 1984 and a record low of 11.08300 in January of 2006. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Custer County, MT - last updated from the United States Federal Reserve on June of 2024.