The largest county in Utah
There are two right answers. By land area it is San Juan County; by population it is Salt Lake County. Which one you want depends on what you meant by largest.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025. Retrieved 30 August 2026.
By land area
| Rank | Name | Land area | Population |
|---|---|---|---|
| 1 | San Juan County | 7,824 sq mi | 14,542 |
| 2 | Tooele County | 7,040 sq mi | 87,461 |
| 3 | Millard County | 6,785 sq mi | 14,057 |
| 4 | Box Elder County | 5,781 sq mi | 65,320 |
| 5 | Garfield County | 5,180 sq mi | 5,256 |
| 6 | Uintah County | 4,483 sq mi | 38,278 |
| 7 | Emery County | 4,463 sq mi | 10,177 |
| 8 | Kane County | 3,994 sq mi | 8,597 |
| 9 | Grand County | 3,673 sq mi | 9,790 |
| 10 | Juab County | 3,392 sq mi | 13,567 |
By population
| Rank | Name | Population | Density |
|---|---|---|---|
| 1 | Salt Lake County | 1,220,916 | 1,622 per sq mi |
| 2 | Utah County | 759,859 | 379 per sq mi |
| 3 | Davis County | 381,227 | 1,174 per sq mi |
| 4 | Weber County | 278,174 | 455 per sq mi |
| 5 | Washington County | 213,670 | 88.0 per sq mi |
| 6 | Cache County | 145,000 | 124 per sq mi |
| 7 | Tooele County | 87,461 | 12.4 per sq mi |
| 8 | Iron County | 67,141 | 20.4 per sq mi |
| 9 | Box Elder County | 65,320 | 11.3 per sq mi |
| 10 | Summit County | 43,141 | 23.1 per sq mi |
And the smallest
More on Utah
Rebuilt from source data 30 August 2026. How these figures are produced.