| Potomac to Opwijk | 3,854.12 mi (6,202.60 km) |
| Potomac to Ostend | 3,796.51 mi (6,109.90 km) |
| Potomac to Oud-Heverlee | 3,877.10 mi (6,239.59 km) |
| Potomac to Oud-Turnhout | 3,877.30 mi (6,239.91 km) |
| Potomac to Oudenaarde | 3,833.45 mi (6,169.34 km) |
| Potomac to Oudenburg | 3,800.82 mi (6,116.83 km) |
| Potomac to Oupeye | 3,919.83 mi (6,308.36 km) |
| Potomac to Overijse | 3,873.00 mi (6,232.99 km) |
| Potomac to Overpelt | 3,897.26 mi (6,272.03 km) |
| Potomac to Paal | 3,892.13 mi (6,263.78 km) |
| Potomac to Peer | 3,900.94 mi (6,277.96 km) |
| Potomac to Pepinster | 3,930.64 mi (6,325.76 km) |
| Potomac to Peruwelz | 3,841.22 mi (6,181.85 km) |
| Potomac to Perwez | 3,888.57 mi (6,258.04 km) |
| Potomac to Philippeville | 3,888.93 mi (6,258.62 km) |
