Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Burley | 1 | 12,275 | 11,759 | 1.06% | 1,816 | 6.8 | City |
| Rupert | 2 | 6,397 | 6,104 | 1.15% | 3,107 | 2.1 | City |
| American Falls | 3 | 4,854 | 4,561 | 1.53% | 3,007 | 1.6 | City |
| Heyburn | 4 | 3,733 | 3,703 | 0.19% | 1,429 | 2.6 | City |
| Oakley | 5 | 825 | 787 | 1.1% | 178 | 4.6 | City |
| Declo | 6 | 359 | 338 | 1.41% | 1,296 | 0.3 | City |
| Albion | 7 | 248 | 235 | 1.22% | 527 | 0.5 | City |
| Malta | 8 | 179 | 166 | 1.7% | 130 | 1.4 | City |
| Acequia | 9 | 137 | 132 | 0.73% | 257 | 0.5 | City |
| Murtaugh | 10 | 122 | 116 | 0.83% | 542 | 0.2 | City |
| Minidoka | 11 | 90 | 89 | 0% | 857 | 0.1 | City |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Burley is the largest city in Cassia County.
Minidoka is the smallest city in Cassia County.
There are 11 cities in Cassia County, Idaho.