County facts · Land area · October 21, 2026
Largest Counties in Montana by Area and Population
The largest Montana counties by land area and by 2023 population, plus the smallest, county seats and a link to each official parcel map.
Looking for the largest counties in Montana? Montana has 56 counties covering about 145,550 square miles of land, based on the Census Bureau's 2020 Gazetteer. The largest by land area is Beaverhead County, at about 5,543 square miles, roughly 7.7 times the size of the smallest, Silver Bow County (718 sq mi). Measured by people instead, the largest is Yellowstone County, with about 170,843 residents in the Census Bureau's July 1, 2023 estimate.
Each table below links the county's Platbookmapper page and its official parcel viewer, so you can go straight from the numbers to the property lines.
Montana counties at a glance
- Counties: 56
- Land area: about 145,550 sq mi, plus about 1,493 sq mi of water inside county lines
- Residents, 2023 estimates: about 1,132,812, or about 7.8 people per square mile of land
- Median county land area: about 2,363 sq mi
- With a verified public parcel viewer in our directory: 56 of 56 (36 of them through a statewide viewer)
The 10 largest Montana counties by land area
| # | County | Seat | Land (sq mi) | 2023 pop. | People per sq mi | Parcel viewer |
|---|---|---|---|---|---|---|
| 1 | Beaverhead County | Dillon | 5,543 | 9,885 | 1.8 | ArcGIS Experience Builder |
| 2 | Phillips County | Malta | 5,140 | 4,249 | 0.8 | Montana Cadastral (Montana State Library) |
| 3 | Flathead County | Kalispell | 5,087 | 113,679 | 22 | ArcGIS Web AppBuilder |
| 4 | Rosebud County | Forsyth | 5,008 | 8,160 | 1.6 | Montana Cadastral (Montana State Library) |
| 5 | Big Horn County | Hardin | 4,998 | 12,751 | 2.6 | Montana Cadastral (Montana State Library) |
| 6 | Valley County | Glasgow | 4,926 | 7,474 | 1.5 | ArcGIS Experience Builder |
| 7 | Garfield County | Jordan | 4,677 | 1,211 | 0.3 | Montana Cadastral (Montana State Library) |
| 8 | Fergus County | Lewistown | 4,339 | 11,772 | 2.7 | Montana Cadastral (Montana State Library) |
| 9 | Blaine County | Chinook | 4,228 | 6,899 | 1.6 | Montana Cadastral (Montana State Library) |
| 10 | Chouteau County | Fort Benton | 3,973 | 5,847 | 1.5 | Montana Cadastral (Montana State Library) |
Together these 10 cover about 33% of Montana's land area and hold about 16% of its residents.
The 10 most populous Montana counties
| # | County | Seat | 2023 pop. | Land (sq mi) | Parcel viewer |
|---|---|---|---|---|---|
| 1 | Yellowstone County | Billings | 170,843 | 2,633 | county web map |
| 2 | Gallatin County | Bozeman | 126,409 | 2,605 | ArcGIS Experience Builder |
| 3 | Missoula County | Missoula | 121,849 | 2,593 | county web map |
| 4 | Flathead County | Kalispell | 113,679 | 5,087 | ArcGIS Web AppBuilder |
| 5 | Cascade County | Great Falls | 84,900 | 2,698 | ArcGIS Experience Builder |
| 6 | Lewis and Clark County | Helena | 75,011 | 3,458 | ArcGIS Web AppBuilder |
| 7 | Ravalli County | Hamilton | 47,738 | 2,391 | ArcGIS Map Viewer |
| 8 | Silver Bow County | Butte | 36,360 | 718 | ArcGIS |
| 9 | Lake County | Polson | 33,338 | 1,490 | ArcGIS Instant Apps |
| 10 | Lincoln County | Libby | 21,895 | 3,613 | ArcGIS Web AppBuilder |
These 10 hold about 73% of Montana's residents in the 2023 estimates.
The 5 smallest Montana counties by land area
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Silver Bow County | Butte | 718 | 36,360 | ArcGIS |
| Deer Lodge County | Anaconda | 737 | 9,673 | Montana Cadastral (Montana State Library) |
| Wibaux County | Wibaux | 890 | 910 | Montana Cadastral (Montana State Library) |
| Treasure County | Hysham | 978 | 772 | Montana Cadastral (Montana State Library) |
| Golden Valley County | Ryegate | 1,174 | 835 | Montana Cadastral (Montana State Library) |
Most and least crowded
- Most people per square mile: Yellowstone County, about 65 (then Silver Bow County, 51, and Gallatin County, 49)
- Fewest people per square mile: Garfield County, about 0.3 (then Petroleum County, 0.3, and Carter County, 0.4)
Counties with the most water
The Census Bureau reports water separately from land. It counts lakes, reservoirs, rivers and, for coastal and Great Lakes counties, the water inside the county boundary.
- Garfield County: about 173 sq mi of water, 4% of its total area
- Flathead County: about 169 sq mi of water, 3% of its total area
- Lake County: about 164 sq mi of water, 10% of its total area
Using these numbers in a land search
- Land area is not parcel count. A large rural county can hold fewer parcels than a small suburban one, so size alone says little about how busy its parcel map is.
- Search, don't scroll. In a big county, type an address, owner name or parcel number into the viewer's search box, where it has one, instead of panning across the map.
- Records follow the county line. Deeds, plats and tax bills are kept by the county where the parcel sits, so a tract that crosses a county line usually has a parcel number in each county.
- Rounded figures. Land and water areas are rounded to whole square miles. People per square mile is the 2023 estimate divided by land area.
Related guides
- Montana county GIS websites by viewer
- Montana landowner maps for hunting
- Idaho–Montana border counties
- Montana–Wyoming border counties
More: All Montana counties on Platbookmapper
Sources
- U.S. Census Bureau Gazetteer files, 2020 county land and water area.
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2023 (July 1, 2023 estimates)
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 21, 2026) for each county's official parcel viewer.
- County seats: Wikidata (county seat property), cross-checked against Census place names.