We found 52 public water systems in Fergus county (ordered by population size).
| Name | Areas served | Population served | Contaminant count | Violation count |
|---|---|---|---|---|
| Lewistown City Of | Lewistown | 5,923 | 0 | 160 |
| Lehrkinds Big Spring Water | Lewistown | 2,575 | 0 | 9 |
| Eddies Corner Inc Moore | Moore | 503 | 0 | 6 |
| Mountain Acres Mb Hm Pk | Lewistown | 320 | 0 | 21 |
| Big Sky Bible College | County of Fergus | 300 | 0 | 0 |
| Denton Town Of | Denton | 255 | 0 | 24 |
| Central Montana Hospital | County of Fergus | 225 | 0 | 0 |
| Winifred Town Of | Winifred | 206 | 0 | 107 |
| Moore Town Of | Moore | 186 | 0 | 10 |
| Roy School District No 74 | County of Fergus | 139 | 0 | 0 |
| Pine Meadows Golf Course Elks 456 The | Lewistown | 130 | 0 | 28 |
| Roy Water Users Assoc | County of Fergus | 125 | 0 | 0 |
| K M Scout Ranch Hilger | County of Fergus | 125 | 0 | 0 |
| Roy Water And Sewer District | Roy | 110 | 0 | 0 |
| Grass Range Town Of | Grass Range | 102 | 0 | 0 |
| Westernaire Drive In Theater | Lewistown | 100 | 0 | 0 |
| Bearpaw Arena | Lewistown | 100 | 0 | 0 |
| Canteen Water Service | Lewistown | 100 | 0 | 0 |
| Big Sky Grocery Unapproved | Moore | 90 | 0 | 0 |
| Hackamore Club | Lewistown | 80 | 0 | 0 |
| Bohemian Corner The | Roy | 79 | 0 | 0 |
| Hi Heat Industries Inc | Lewistown | 75 | 0 | 0 |
| King Ranch Colony | Lewistown | 56 | 0 | 0 |
| Us Gypsum | County of Fergus | 55 | 0 | 0 |
| Deerfield Hutterite Colony | Lewistown | 51 | 0 | 0 |
| Central Montana Jaycees | County of Fergus | 50 | 0 | 0 |
| Roy Bar | County of Fergus | 50 | 0 | 0 |
| Spring Creek Colony Lewistown | Lewistown | 48 | 0 | 0 |
| Ayers Hutterite Colony | Grass Range | 46 | 0 | 0 |
| Crystal Lake Cg And Guard Station | Lewistown | 40 | 0 | 0 |
| Rainbow Bar | Hilger | 31 | 0 | 0 |
| Ken Glass Water | Denton | 30 | 0 | 0 |
| Lazy Kx Bar | Roy | 27 | 0 | 0 |
| Shirey Pub | Hilger | 26 | 0 | 0 |
| Culligan Water Lewistown | County of Fergus | 25 | 0 | 0 |
| Lazy Kx Bar | County of Fergus | 25 | 0 | 0 |
| James Kipp Campground Blm | Lewistown | 25 | 0 | 0 |
| Fry Brothers Inc | Lewistown | 25 | 0 | 0 |
| Roy American Legion | County of Fergus | 25 | 0 | 0 |
| Boulevard Apartments | County of Fergus | 25 | 0 | 0 |
| Lewistown Sports & Courts | County of Fergus | 25 | 0 | 0 |
| School District # 11 | County of Fergus | 25 | 0 | 0 |
| Judith Shadows Golf Course | Lewistown | 25 | 0 | 0 |
| Brooks School | County of Fergus | 25 | 0 | 0 |
| Coffee Creek Water Company | Coffee Creek | 24 | 0 | 0 |
| Sawyer's Trailer Court | County of Fergus | 24 | 0 | 0 |
| Maiden School | County of Fergus | 22 | 0 | 0 |
| School District 56 | County of Fergus | 20 | 0 | 0 |
| Brooks School | County of Fergus | 15 | 0 | 0 |
| Kiwanis Rv Park | County of Fergus | 10 | 0 | 0 |
| Cottonwood School | County of Fergus | 7 | 0 | 0 |
| Albertsons Lewistown No 2019 | Lewistown | 0 | 0 | 0 |