| Difficult Run to Florence (South Carolina) | 353.38 mi (568.71 km) |
| Difficult Run to Florence-Graham (California) | 2,279.60 mi (3,668.67 km) |
| Difficult Run to Florham Park (New Jersey) | 203.25 mi (327.10 km) |
| Difficult Run to Florida (Puerto Rico) | 1,559.60 mi (2,509.94 km) |
| Difficult Run to Florida City (Florida) | 947.55 mi (1,524.94 km) |
| Difficult Run to Florida Ridge (Florida) | 801.52 mi (1,289.93 km) |
| Difficult Run to Florin (California) | 2,352.44 mi (3,785.88 km) |
| Difficult Run to Florissant (Missouri) | 697.87 mi (1,123.12 km) |
| Difficult Run to Flower Hill (Maryland) | 20.39 mi (32.82 km) |
| Difficult Run to Flower Mound (Texas) | 1,174.43 mi (1,890.07 km) |
| Difficult Run to Flowing Wells (Arizona) | 1,933.85 mi (3,112.23 km) |
| Difficult Run to Foley (Alabama) | 829.02 mi (1,334.18 km) |
| Difficult Run to Folsom (California) | 2,335.53 mi (3,758.67 km) |
| Difficult Run to Fond du Lac (Wisconsin) | 665.79 mi (1,071.48 km) |
| Difficult Run to Fontana (California) | 2,234.40 mi (3,595.93 km) |
