Resident Population in Granite County, MT was 3.59500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Granite County, MT reached a record high of 3.59500 in January of 2023 and a record low of 2.52800 in January of 1990. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Granite County, MT - last updated from the United States Federal Reserve on May of 2024.