| Difficult Run to Silver Firs (Washington) | 2,298.41 mi (3,698.94 km) |
| Difficult Run to Silver Spring (Maryland) | 18.88 mi (30.39 km) |
| Difficult Run to Silver Springs Shores (Florida) | 726.99 mi (1,169.97 km) |
| Difficult Run to Silverdale (Washington) | 2,323.54 mi (3,739.37 km) |
| Difficult Run to Silverton (Oregon) | 2,340.85 mi (3,767.23 km) |
| Difficult Run to Simi Valley (California) | 2,299.42 mi (3,700.56 km) |
| Difficult Run to Simpsonville (South Carolina) | 395.96 mi (637.23 km) |
| Difficult Run to Sioux City (Iowa) | 1,025.56 mi (1,650.48 km) |
| Difficult Run to Sioux Falls (South Dakota) | 1,054.27 mi (1,696.68 km) |
| Difficult Run to Skokie (Illinois) | 587.15 mi (944.93 km) |
| Difficult Run to Sleepy Hollow (New York) | 238.22 mi (383.38 km) |
| Difficult Run to Slidell (Louisiana) | 922.76 mi (1,485.04 km) |
| Difficult Run to Smithfield (North Carolina) | 240.51 mi (387.07 km) |
| Difficult Run to Smithfield (Utah) | 1,814.08 mi (2,919.48 km) |
| Difficult Run to Smithville (Missouri) | 922.35 mi (1,484.37 km) |
