County outline
Where Prairie County is located
Area breakdown
Land accounts for 99.7% of Prairie County’s measured area and water for 0.3%. Its combined area converts to 4,512.9 square kilometers or approximately 1,115,155 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,736.603 | 4,497.781 | 1,111,425.9 |
| Water | 5.827 | 15.092 | 3,729.3 |
| Total | 1,742.43 | 4,512.873 | 1,115,155.2 |
How Prairie County compares
By original Census land area, Prairie County ranks #39 of 56 in Montana and #343 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.735 times the Montana county-equivalent median of 2,363.3 square miles. It accounts for 1.2% of the combined county land area in the state.
See the complete Montana ranking · What counts as a county equivalent?
Population and density of Prairie County
The Census Bureau estimates that 1,112 people lived in Prairie County on July 1, 2025. That ranks #3,181 of 3,222 county equivalents nationally and #52 of 56 in Montana. Since the April 1, 2020 estimates base of 1,094, the population has grown by 18 (+1.6%), compared with +5.6% for Montana as a whole.
With 1,736.6 square miles of land, that is 0.64 people per square mile (0.25 per km²), placing Prairie County #3,186 nationally for density and #52 in Montana. The median county equivalent has 47 people per square mile; the Montana median is 2.8. Put another way, there are about 999 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 1,094 | 1,099 | 1,113 | 1,112 | 1,108 | 1,112 |
| Change | — | +5 | +14 | −1 | −4 | +4 |
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 Prairie County
1 incorporated place lies at least partly in Prairie County. Together they are home to 574 people (51.6%); the other 538 (48.4%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Terry town, with 574 residents in the county.
Metropolitan area
Prairie County is not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.
ZIP codes
7 ZIP Code Tabulation Areas have land in Prairie County; 2 of them have most of their land inside the county, and the others mainly cover neighboring areas.
59214593015932659330593365933959349
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 Prairie County
Prairie County shares a land border with 6 county equivalents. It has more land than 2 of them. The largest neighbor is Garfield County (4,676.6 mi²) and the smallest is Wibaux County (889.6 mi²). Together with its neighbors, Prairie County forms a block of 17,720.8 mi² of land, of which it holds 9.8%.
| Bordering county equivalent | Land mi² | Size vs. Prairie | Compare |
|---|---|---|---|
| Garfield County | 4,676.6 | 2.7× larger | Compare |
| Custer County | 3,783.3 | 2.2× larger | Compare |
| McCone County | 2,642.2 | 1.5× larger | Compare |
| Dawson County | 2,371.9 | 1.4× larger | Compare |
| Fallon County | 1,620.6 | 1.1× smaller | Compare |
| Wibaux County | 889.6 | 2× smaller | Compare |
How big is Prairie County compared with U.S. states?
Prairie 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 84 areas the size of Prairie County.
Another way to picture it: the same land area would fill a square about 41.7 miles (67.1 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 Prairie County?
Prairie County has more land than 2,879 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 Prairie County at #387 nationally by total area, 44 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 0.3%, compared with a national county-equivalent median of 1.2% — 0.8 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 Prairie County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #342 | Clallam County, Washington | 1,738.8 | Compare |
| #343 | Prairie County, Montana | 1,736.6 | This county |
| #344 | Bonner County, Idaho | 1,733.2 | Compare |
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.
Representative coordinates
The Census internal point is 46.812388, -105.503938. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 4,497,780,198 m²; AWATER: 15,092,929 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Prairie County?
Prairie County, Montana has 1,736.6 square miles (4,497.8 km²) of land and 5.827 square miles of water, for a total area of 1,742.4 square miles. It ranks #343 of 3,222 U.S. county equivalents by land area.
Is Prairie County the largest county in Montana?
No. Prairie County ranks #39 of 56 in Montana by land area. The largest is Beaverhead County, with 5,542.7 square miles of land.
What counties border Prairie County?
Prairie County shares a land border with Custer County, Dawson County, McCone County, Garfield County, Wibaux County, and Fallon County.
What is the population of Prairie County?
The Census Bureau estimates Prairie County had 1,112 residents on July 1, 2025, ranking #3,181 of 3,222 county equivalents. That is 0.64 people per square mile of land.
What is the county seat of Prairie County?
The county seat of Prairie County is Terry.
Is Prairie County part of a metropolitan area?
No. Prairie County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Prairie County?
7 ZIP Code Tabulation Areas have land in Prairie County, and 2 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Prairie County compare with U.S. states?
It has more land than 1 of the 50 states, including Rhode Island (1,033.9 square miles of land).
How many acres of land are in Prairie County?
The land measurement converts to approximately 1,111,426 acres. Including water, total area is approximately 1,115,155 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.