County facts · Population · October 25, 2026
Montana Population by County, 2025 Census Estimates
Montana population by county: July 2025 Census estimates for all 56 counties, change since 2020, density, and a link to each official parcel map.
Looking for Montana population by county? The Census Bureau estimates that Montana had 1,144,694 residents on July 1, 2025, spread across 56 counties. Yellowstone County is the most populous, with 172,692 people (15% of the state), and Petroleum County is the least populous, with 548.
The table below lists every county with its 2025 estimate, its April 2020 starting point, the change, people per square mile, and a link to its official parcel viewer.
Montana population at a glance
- Counties: 56
- Statewide, July 1, 2025: 1,144,694 (April 1, 2020 estimates base: 1,084,221; change +60,473, +5.6%)
- Most populous: Yellowstone County (172,692); least populous: Petroleum County (548)
- Median county: about 7,819 residents (half of the counties are smaller)
- The 5 largest counties hold 55% of all Montana residents
- Counties with 1,000,000+ residents: 0 · 100,000+: 4 · under 10,000: 33
- Statewide density: about 7.9 people per square mile of land
Montana population by county, July 2025 (all 56)
Percent change runs from the April 1, 2020 estimates base to July 1, 2025. People per square mile is the July 2025 estimate divided by the county's land area in the Census Bureau's 2020 Gazetteer file, so lakes and bays are left out.
How Montana's population is spread out
Grouping the counties by size shows how concentrated the state is:
| Residents (July 2025) | Counties | Total residents | Share of state |
|---|---|---|---|
| 100,000 to 249,999 | 4 | 540,374 | 47% |
| 25,000 to 99,999 | 5 | 278,452 | 24% |
| 10,000 to 24,999 | 14 | 187,328 | 16% |
| Under 10,000 | 33 | 138,540 | 12% |
Most and least densely populated
The most crowded counties by people per square mile of land:
- Yellowstone County: 66 per sq mi (172,692 people on 2,633 sq mi)
- Silver Bow County: 50 per sq mi (36,118 people on 718 sq mi)
- Gallatin County: 49 per sq mi (128,740 people on 2,605 sq mi)
- Missoula County: 48 per sq mi (123,513 people on 2,593 sq mi)
- Cascade County: 32 per sq mi (85,029 people on 2,698 sq mi)
The most thinly settled:
- Garfield County: 0.2 per sq mi (1,148 people on 4,677 sq mi)
- Petroleum County: 0.3 per sq mi (548 people on 1,656 sq mi)
- Carter County: 0.4 per sq mi (1,383 people on 3,340 sq mi)
- Powder River County: 0.5 per sq mi (1,781 people on 3,298 sq mi)
- Prairie County: 0.6 per sq mi (1,112 people on 1,737 sq mi)
About these numbers
- They are estimates. Between censuses the Census Bureau's Population Estimates Program updates county totals each year from births, deaths and migration records. The next full count is the 2030 census.
- The base is April 1, 2020. The estimates start from an April 1, 2020 "estimates base" built from the 2020 census, which is why it is slightly different from the published census count.
- Each new release revises the past. A newer vintage can change earlier years as well, so compare numbers from the same release, as this page does.
- Statewide total. The counties add up exactly to the statewide figure of 1,144,694 in the same file.
Using population numbers in a land search
- Big counties, busy offices. In the most populous counties, parcel maps and deed records are usually online and searchable, but recording and permit offices are busier. Allow for that if you are on a deadline.
- Small counties, fewer sales. In counties with only a few thousand people, land changes hands less often, so there are fewer recent sales to compare a price with. Recorded deeds and the local assessor's sales records are the best source.
- Density hints at lot size. A low people-per-square-mile figure usually means farms, ranches and timber tracts; a high one means subdivided lots. The parcel viewer shows the actual parcel lines.
- Check the official map. Use the parcel viewer link in the table for boundaries, parcel numbers and owner names, then confirm anything important with the local assessor and the office that records deeds.
Related guides
- Fastest growing counties in Montana
- Largest counties in Montana
- Montana county GIS websites by viewer
- Montana landowner maps for hunting
- Most populous counties in the US
- Where people are moving in the US
More: All Montana counties on Platbookmapper
Sources
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2025 (April 1, 2020 estimates base and July 1, 2020–2025 estimates, with components of change). Statewide totals are the sum of the counties and match the file's state row.
- U.S. Census Bureau Gazetteer files, 2020 county land and water area (for people per square mile).
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 25, 2026) for each official parcel viewer.