There are 7 cities in Petroleum County, Montana.
Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Population | 2020 Population | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Roundup | 1 | 2,030 | 1,748 | 3.57% | 1,570 | 1.3 | City |
| Klein | 2 | 275 | 156 | 2.61% | 21 | 12.9 | CDP |
| Winnett | 3 | 216 | 188 | 3.35% | 212 | 1.0 | Town |
| Camp Three | 4 | 152 | 150 | -1.3% | 34 | 4.5 | CDP |
| Grass Range | 5 | 116 | 112 | 0.87% | 829 | 0.1 | Town |
| Fords Creek Colony | 6 | 62 | 43 | 8.77% | 356 | 0.2 | CDP |
| Ayers Ranch Colony | 7 | 46 | 66 | 9.52% | 105 | 0.4 | CDP |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Roundup is the largest city in Petroleum County.
Ayers Ranch Colony is the smallest city in Petroleum County.
There are 7 cities in Petroleum County, Montana.