| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Carrington | 1 | 1,928 | 2,075 | -1.13% | 813 | 2 | City |
| Glenfield | 2 | 93 | 95 | 0% | 679 | 0 | City |
| McHenry | 3 | 59 | 63 | -1.67% | 240 | 0 | City |
| Grace City | 4 | 51 | 54 | -1.92% | 208 | 0 | City |
Carrington is the largest city in Foster County, with a population of 1,928.
Grace City is the smallest city in Foster County, with a population of 51.
There are 4 cities in Foster County, North Dakota.