Founded in February 26, 1883, Yellowstone County is one of 56 counties in the state of Montana. Historically, Yellowstone County was formed from Custer County. The city of Billings is the county seat. With FIPS code of 111, Yellowstone County has a population of 167,146 and area of 2,635 square miles (6,825 km2).
List of all cities in Yellowstone County, MT alphabetically
| City/Town | Postal Code | Area Code |
| Acton, MT | 59002 | 406 |
| Ballantine, MT | 59006 | 406 |
| Billings, MT | 59101 | 406 |
| 59102 | 406 | |
| 59103 | 406 | |
| 59104 | 406 | |
| 59105 | 406 | |
| 59106 | 406 | |
| 59107 | 406 | |
| 59108 | 406 | |
| 59111 | 406 | |
| 59112 | 406 | |
| 59114 | 406 | |
| 59115 | 406 | |
| 59116 | 406 | |
| 59117 | 406 | |
| Broadview, MT | 59015 | 406 |
| Comanche, MT | 59015 | 406 |
| Custer, MT | 59024 | 406 |
| First Interstate Bank, MT | 59116 | 406 |
| Hesper, MT | 59102 | 406 |
| Huntley, MT | 59037 | 406 |
| K O A, MT | 59114 | 406 |
| Laurel, MT | 59044 | 406 |
| Lockwood, MT | 59101 | 406 |
| Molt, MT | 59002 | 406 |
| 59057 | 406 | |
| Mount Dakota Util Co, MT | 59112 | 406 |
| Pompeys Pillar, MT | 59064 | 406 |
| Public Works, MT | 59111 | 406 |
| Shepherd, MT | 59079 | 406 |
| Us Bank, MT | 59115 | 406 |
| Wells Fargo Bank, MT | 59117 | 406 |
| Worden, MT | 59088 | 406 |