| Potomac to Nuth | 3,923.92 mi (6,314.94 km) |
| Potomac to Oegstgeest | 3,834.75 mi (6,171.43 km) |
| Potomac to Oirschot | 3,885.20 mi (6,252.63 km) |
| Potomac to Oisterwijk | 3,879.06 mi (6,242.74 km) |
| Potomac to Oldebroek | 3,884.32 mi (6,251.21 km) |
| Potomac to Oldenzaal | 3,928.14 mi (6,321.74 km) |
| Potomac to Ommen | 3,902.75 mi (6,280.87 km) |
| Potomac to Oosterend | 3,876.62 mi (6,238.81 km) |
| Potomac to Oosterhout | 3,863.86 mi (6,218.28 km) |
| Potomac to Oosterwolde | 3,885.65 mi (6,253.35 km) |
| Potomac to Oostzaan | 3,844.92 mi (6,187.80 km) |
| Potomac to Opmeer | 3,840.88 mi (6,181.30 km) |
| Potomac to Oss | 3,886.89 mi (6,255.35 km) |
| Potomac to Oud-Beijerland | 3,841.27 mi (6,181.93 km) |
| Potomac to Oudenbosch | 3,851.95 mi (6,199.11 km) |
