| Difficult Run to Ukiah (California) | 2,434.87 mi (3,918.55 km) |
| Difficult Run to Union (Missouri) | 736.11 mi (1,184.65 km) |
| Difficult Run to Union City (California) | 2,400.94 mi (3,863.93 km) |
| Difficult Run to Union City (Georgia) | 543.84 mi (875.22 km) |
| Difficult Run to Union City (New Jersey) | 218.04 mi (350.89 km) |
| Difficult Run to Union City (Tennessee) | 661.86 mi (1,065.16 km) |
| Difficult Run to Union Hill-Novelty Hill (Washington) | 2,293.08 mi (3,690.35 km) |
| Difficult Run to Union Park (Florida) | 748.06 mi (1,203.89 km) |
| Difficult Run to Uniondale (New York) | 235.36 mi (378.77 km) |
| Difficult Run to Universal City (Texas) | 1,355.87 mi (2,182.05 km) |
| Difficult Run to University (Florida) | 802.90 mi (1,292.14 km) |
| Difficult Run to University City (Missouri) | 698.93 mi (1,124.82 km) |
| Difficult Run to University Heights (Ohio) | 284.46 mi (457.79 km) |
| Difficult Run to University of California-Santa Barbara (California) | 2,355.15 mi (3,790.25 km) |
| Difficult Run to University Park (Texas) | 1,163.33 mi (1,872.21 km) |
