| Potomac to Sesimbra | 3,578.92 mi (5,759.71 km) |
| Potomac to Setubal | 3,586.97 mi (5,772.67 km) |
| Potomac to Sever do Vouga | 3,553.67 mi (5,719.09 km) |
| Potomac to Silves | 3,647.21 mi (5,869.62 km) |
| Potomac to Sines | 3,604.18 mi (5,800.37 km) |
| Potomac to Sintra | 3,554.89 mi (5,721.05 km) |
| Potomac to Sobrado de Paiva | 3,550.76 mi (5,714.39 km) |
| Potomac to Sobral de Monte Agraco | 3,560.66 mi (5,730.34 km) |
| Potomac to Soure | 3,558.59 mi (5,726.99 km) |
| Potomac to Tabua | 3,579.84 mi (5,761.20 km) |
| Potomac to Tavira | 3,688.69 mi (5,936.38 km) |
| Potomac to Tomar | 3,581.18 mi (5,763.35 km) |
| Potomac to Tondela | 3,573.09 mi (5,750.33 km) |
| Potomac to Torre de Moncorvo | 3,601.09 mi (5,795.40 km) |
| Potomac to Torres Novas | 3,579.04 mi (5,759.91 km) |
