Stillwater County area

Population and density of Stillwater County

The Census Bureau estimates that 9,445 people lived in Stillwater County on July 1, 2025. That ranks #2,525 of 3,222 county equivalents nationally and #25 of 56 in Montana. Since the April 1, 2020 estimates base of 8,960, the population has grown by 485 (+5.4%), compared with +5.6% for Montana as a whole.

With 1,796.5 square miles of land, that is 5.3 people per square mile (2 per km²), placing Stillwater County #2,836 nationally for density and #18 in Montana. The median county equivalent has 47 people per square mile; the Montana median is 2.8. Put another way, there are about 122 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Stillwater County

1 incorporated place lies at least partly in Stillwater County. Together they are home to 1,964 people (20.8%); the other 7,481 (79.2%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Columbus town, with 1,964 residents in the county.

Metropolitan area

Stillwater County is an outlying county of the Billings, MT Metropolitan Statistical Area. Its 3 county equivalents have 193,603 residents on 6,477.8 square miles of land; Stillwater County accounts for 27.7% of the land and 4.9% of the residents. By combined land it ranks #29 of 393 metropolitan areas, and #242 by population.

ZIP codes

10 ZIP Code Tabulation Areas have land in Stillwater County; 8 of them have most of their land inside the county, and the others mainly cover neighboring areas.

59001590155901959028590575906159063590675906959074

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Stillwater County

Stillwater County shares a land border with 5 county equivalents. It has more land than 1 of them. The largest neighbor is Park County (2,802.5 mi²) and the smallest is Golden Valley County (1,174.4 mi²). Together with its neighbors, Stillwater County forms a block of 12,310.3 mi² of land, of which it holds 14.6%.

How big is Stillwater County compared with U.S. states?

Stillwater County has more land than 1 of the 50 states. It is about 1.7 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.1 times as much land (1,948.6 mi²). Montana’s county land could hold about 81 areas the size of Stillwater County.

Another way to picture it: the same land area would fill a square about 42.4 miles (68.2 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Stillwater County?

Stillwater County has more land than 2,893 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Stillwater County at #368 nationally by total area, 39 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 0.5%, compared with a national county-equivalent median of 1.2% — 0.7 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Stillwater County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.