| Potomac to Montalegre | 3,553.43 mi (5,718.70 km) |
| Potomac to Montemor-o-Novo | 3,616.96 mi (5,820.93 km) |
| Potomac to Montemor-o-Velho | 3,553.07 mi (5,718.11 km) |
| Potomac to Montijo | 3,582.24 mi (5,765.05 km) |
| Potomac to Mortagua | 3,567.99 mi (5,742.13 km) |
| Potomac to Moura | 3,669.40 mi (5,905.33 km) |
| Potomac to Murtosa | 3,540.73 mi (5,698.26 km) |
| Potomac to Nazare | 3,549.27 mi (5,712.00 km) |
| Potomac to Nelas | 3,584.42 mi (5,768.57 km) |
| Potomac to Obidos | 3,551.24 mi (5,715.16 km) |
| Potomac to Odemira | 3,626.17 mi (5,835.76 km) |
| Potomac to Odivelas | 3,565.47 mi (5,738.06 km) |
| Potomac to Oeiras | 3,561.59 mi (5,731.83 km) |
| Potomac to Olhao | 3,681.78 mi (5,925.26 km) |
| Potomac to Oliveira de Azemeis | 3,545.66 mi (5,706.19 km) |
