| Difficult Run to Cullman (Alabama) | 619.39 mi (996.81 km) |
| Difficult Run to Culpeper (Virginia) | 46.13 mi (74.24 km) |
| Difficult Run to Culver City (California) | 2,286.84 mi (3,680.32 km) |
| Difficult Run to Cumberland (Maryland) | 91.55 mi (147.34 km) |
| Difficult Run to Cupertino (California) | 2,408.05 mi (3,875.38 km) |
| Difficult Run to Cutler Bay (Florida) | 936.93 mi (1,507.85 km) |
| Difficult Run to Cutlerville (Michigan) | 512.76 mi (825.21 km) |
| Difficult Run to Cuyahoga Falls (Ohio) | 270.48 mi (435.30 km) |
| Difficult Run to Cypress (California) | 2,272.25 mi (3,656.83 km) |
| Difficult Run to Cypress Gardens (Florida) | 793.15 mi (1,276.45 km) |
| Difficult Run to Cypress Lake (Florida) | 893.87 mi (1,438.55 km) |
| Difficult Run to D'Iberville (Mississippi) | 876.27 mi (1,410.21 km) |
| Difficult Run to Dakota Ridge (Colorado) | 1,481.44 mi (2,384.14 km) |
| Difficult Run to Dale City (Virginia) | 17.57 mi (28.28 km) |
| Difficult Run to Dallas (Georgia) | 540.37 mi (869.64 km) |
