| # | County | State | Population | Change since 2020 | Unemployment rate |
|---|
| 1 | Uinta County | Wyoming | 20,621 | 0.8 % | 3.6 % |
| 2 | Uintah County | Utah | 38,307 | 7.6 % | 3.7 % |
| 3 | Ulster County | New York | 182,977 | 0.6 % | 3.6 % |
| 4 | Umatilla County | Oregon | 80,491 | 0.5 % | 5.6 % |
| 5 | Unicoi County | Tennessee | 17,872 | -0.2 % | 4.6 % |
| 6 | Union County | New Jersey | 594,160 | 3.3 % | 5.5 % |
| 7 | Union County | North Carolina | 263,386 | 10.6 % | 3.4 % |
| 8 | Union County | Ohio | 71,721 | 14.2 % | 3.6 % |
| 9 | Union County | Pennsylvania | 42,159 | -1.2 % | 4.1 % |
| 10 | Union County | Arkansas | 37,008 | -5.2 % | 5.4 % |
| 11 | Union County | Mississippi | 28,363 | 2.1 % | 3.2 % |
| 12 | Union County | Georgia | 27,601 | 12.1 % | 3.7 % |
| 13 | Union County | South Carolina | 26,678 | -2.1 % | 5.9 % |
| 14 | Union County | Oregon | 26,058 | -0.5 % | 5.7 % |
| 15 | Union County | Tennessee | 21,064 | 6.4 % | 3.7 % |
| 16 | Union County | South Dakota | 17,402 | 3.5 % | 2.1 % |
| 17 | Union County | Illinois | 16,886 | -2.7 % | 4.6 % |
| 18 | Union County | Florida | 15,738 | -2.5 % | 5.3 % |
| 19 | Union County | Kentucky | 13,178 | -3.6 % | 4.2 % |
| 20 | Union County | Iowa | 11,955 | -1.5 % | 3.5 % |
| 21 | Union County | Indiana | 6,884 | -2.8 % | 2.7 % |
| 22 | Union County | New Mexico | 3,926 | -3.9 % | 3.6 % |
| 23 | Union Parish | Louisiana | 20,617 | -2.3 % | 5.1 % |
| 24 | Upshur County | Texas | 44,050 | 7.7 % | 4.4 % |
| 25 | Upshur County | West Virginia | 23,650 | -0.7 % | 4.9 % |
| 26 | Upson County | Georgia | 28,358 | 2.4 % | 3.4 % |
| 27 | Upton County | Texas | 3,128 | -5.5 % | 1.8 % |
| 28 | Utah County | Utah | 747,234 | 13.3 % | 3.6 % |
| 29 | Uvalde County | Texas | 25,138 | 2.3 % | 4.3 % |