| Dorchester to Olympia Heights (Florida) | 4,346.17 mi (6,994.49 km) |
| Dorchester to Omaha (Nebraska) | 4,234.40 mi (6,814.60 km) |
| Dorchester to On Top of the World Designated Place (Florida) | 4,263.50 mi (6,861.44 km) |
| Dorchester to Onalaska (Wisconsin) | 3,930.12 mi (6,324.91 km) |
| Dorchester to Oneida (New York) | 3,353.71 mi (5,397.28 km) |
| Dorchester to Oneonta (New York) | 3,354.65 mi (5,398.79 km) |
| Dorchester to Ontario (California) | 5,380.36 mi (8,658.86 km) |
| Dorchester to Ontario (Oregon) | 4,807.75 mi (7,737.32 km) |
| Dorchester to Opa-locka (Florida) | 4,333.83 mi (6,974.63 km) |
| Dorchester to Opelika (Alabama) | 4,221.86 mi (6,794.42 km) |
| Dorchester to Opelousas (Louisiana) | 4,604.35 mi (7,409.98 km) |
| Dorchester to Orange (California) | 5,400.78 mi (8,691.72 km) |
| Dorchester to Orange (Texas) | 4,693.32 mi (7,553.16 km) |
| Dorchester to Orange City (Florida) | 4,229.11 mi (6,806.09 km) |
| Dorchester to Orangeburg (South Carolina) | 3,992.89 mi (6,425.94 km) |
