| Niagara Falls to Nuth | 3,811.40 mi (6,133.86 km) |
| Niagara Falls to Oegstgeest | 3,717.63 mi (5,982.95 km) |
| Niagara Falls to Oirschot | 3,770.50 mi (6,068.04 km) |
| Niagara Falls to Oisterwijk | 3,764.07 mi (6,057.69 km) |
| Niagara Falls to Oldebroek | 3,763.73 mi (6,057.14 km) |
| Niagara Falls to Oldenzaal | 3,806.74 mi (6,126.36 km) |
| Niagara Falls to Ommen | 3,781.06 mi (6,085.04 km) |
| Niagara Falls to Oosterend | 3,752.88 mi (6,039.68 km) |
| Niagara Falls to Oosterhout | 3,749.06 mi (6,033.53 km) |
| Niagara Falls to Oosterwolde | 3,761.67 mi (6,053.82 km) |
| Niagara Falls to Oostzaan | 3,725.87 mi (5,996.21 km) |
| Niagara Falls to Opmeer | 3,720.32 mi (5,987.27 km) |
| Niagara Falls to Oss | 3,770.46 mi (6,067.97 km) |
| Niagara Falls to Oud-Beijerland | 3,726.22 mi (5,996.76 km) |
| Niagara Falls to Oudenbosch | 3,737.93 mi (6,015.62 km) |
