| Difficult Run to Castle Pines (Colorado) | 1,468.84 mi (2,363.88 km) |
| Difficult Run to Castle Rock (Colorado) | 1,468.71 mi (2,363.66 km) |
| Difficult Run to Castro Valley (California) | 2,401.24 mi (3,864.41 km) |
| Difficult Run to Catalina Foothills (Arizona) | 1,926.73 mi (3,100.77 km) |
| Difficult Run to Cataño (Puerto Rico) | 1,565.49 mi (2,519.41 km) |
| Difficult Run to Cathedral City (California) | 2,187.29 mi (3,520.10 km) |
| Difficult Run to Catonsville (Maryland) | 41.00 mi (65.98 km) |
| Difficult Run to Cave Spring (Virginia) | 185.33 mi (298.26 km) |
| Difficult Run to Cayce (South Carolina) | 399.23 mi (642.50 km) |
| Difficult Run to Cayey (Puerto Rico) | 1,585.52 mi (2,551.65 km) |
| Difficult Run to Cedar City (Utah) | 1,927.97 mi (3,102.77 km) |
| Difficult Run to Cedar Falls (Iowa) | 828.40 mi (1,333.17 km) |
| Difficult Run to Cedar Hill (Texas) | 1,180.34 mi (1,899.57 km) |
| Difficult Run to Cedar Lake (Indiana) | 559.30 mi (900.10 km) |
| Difficult Run to Cedar Mill (Oregon) | 2,338.24 mi (3,763.03 km) |
