Founded in February 2, 1865, Gallatin County is one of 56 counties in the state of Montana. Historically, Gallatin County was one of the 9 original counties. The city of Bozeman is the county seat. With FIPS code of 31, Gallatin County has a population of 122,713 and area of 2,507 square miles (6,493 km2).
List of all cities in Gallatin County, MT alphabetically
| City/Town | Postal Code | Area Code |
| Amsterdam, MT | 59741 | 406 |
| Belgrade, MT | 59714 | 406 |
| Big Sky, MT | 59716 | 406 |
| Bozeman, MT | 59715 | 406 |
| 59717 | 406 | |
| 59718 | 406 | |
| 59719 | 406 | |
| 59771 | 406 | |
| 59772 | 406 | |
| Gallatin Gateway, MT | 59730 | 406 |
| Gallatin Gtwy, MT | 59730 | 406 |
| Manhattan, MT | 59741 | 406 |
| Montana State University Bozeman, MT | 59717 | 406 |
| Three Forks, MT | 59752 | 406 |
| Trident, MT | 59752 | 406 |
| West Yellowstone, MT | 59758 | 406 |
| Willow Creek, MT | 59760 | 406 |