| Merthyr Tudful to Silver Firs (Washington) | 4,665.24 mi (7,507.98 km) |
| Merthyr Tudful to Silver Spring (Maryland) | 3,521.76 mi (5,667.73 km) |
| Merthyr Tudful to Silver Springs Shores (Florida) | 4,197.40 mi (6,755.06 km) |
| Merthyr Tudful to Silverdale (Washington) | 4,690.77 mi (7,549.07 km) |
| Merthyr Tudful to Silverton (Oregon) | 4,843.62 mi (7,795.05 km) |
| Merthyr Tudful to Simi Valley (California) | 5,328.67 mi (8,575.66 km) |
| Merthyr Tudful to Simpsonville (South Carolina) | 3,934.25 mi (6,331.56 km) |
| Merthyr Tudful to Sioux City (Iowa) | 4,115.96 mi (6,624.00 km) |
| Merthyr Tudful to Sioux Falls (South Dakota) | 4,078.23 mi (6,563.27 km) |
| Merthyr Tudful to Skokie (Illinois) | 3,812.68 mi (6,135.92 km) |
| Merthyr Tudful to Sleepy Hollow (New York) | 3,301.46 mi (5,313.18 km) |
| Merthyr Tudful to Slidell (Louisiana) | 4,460.65 mi (7,178.72 km) |
| Merthyr Tudful to Smithfield (North Carolina) | 3,735.71 mi (6,012.05 km) |
| Merthyr Tudful to Smithfield (Utah) | 4,684.90 mi (7,539.62 km) |
| Merthyr Tudful to Smithville (Missouri) | 4,198.71 mi (6,757.17 km) |
