Cities and Counties Information

Updated: February 2, 2026

Montana became a territory in 1864 and a state in 1889. Beaverhead, Chouteau, Deer Lodge, Jefferson, Lewis and Clark, Madison, and Missoula counties were established in 1865. The rest of the counties were created thereafter, the last, Petroleum County, being established in 1925. The largest county in terms of area is Beaverhead County, encompassing about 5,572 square miles in total (about 5,542 square miles of land and 30 square miles of water), slightly larger than the state of Connecticut. The smallest, only about 718 square miles, is Silver Bow County.

The greatest population density in the state can still be found in Yellowstone County, which contains Billings, Montana's largest and most populated city. According to recent estimates, Yellowstone County now has a population of roughly 170,000-173,000 people, and a density of about 60 people per square mile?by far the highest in Montana. That is a lot for one county, considering Montana has 56 counties in all and a total state population of about 1.15 million people in 2026.

For more information, visit the Census and Economic Information Center (CEIC) at the Montana Department of Commerce, the state's designated data center for the U.S. Census Bureau and the official source of detailed census and economic data for Montana. CEIC maintains online tools and documents about the population of the state, historical as well as current, including city- and county-level census data and interactive dashboards.

Try our License Plate Game to learn all the counties!

Updated: February 2, 2026