| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Idaho Falls | 1 | 72,700 | 65,908 | 1.27% | 2,677 | 27 | City |
| Ammon | 2 | 20,681 | 17,877 | 2.79% | 2,530 | 8 | City |
| Iona | 3 | 3,271 | 2,751 | 2.89% | 2,598 | 1 | City |
| Ucon | 4 | 1,209 | 1,169 | 1.09% | 1,326 | 1 | City |
| Swan Valley | 5 | 338 | 243 | 5.3% | 29 | 12 | City |
| Irwin | 6 | 308 | 265 | 1.99% | 118 | 3 | City |
Idaho Falls is the largest city in Bonneville County, with a population of 72,700.
Irwin is the smallest city in Bonneville County, with a population of 308.
There are 6 cities in Bonneville County, Idaho.