| Mortara to Olympia Heights (Florida) | 4,935.88 mi (7,943.53 km) |
| Mortara to Omaha (Nebraska) | 4,873.76 mi (7,843.56 km) |
| Mortara to On Top of the World Designated Place (Florida) | 4,868.91 mi (7,835.75 km) |
| Mortara to Onalaska (Wisconsin) | 4,569.39 mi (7,353.73 km) |
| Mortara to Oneida (New York) | 3,983.12 mi (6,410.21 km) |
| Mortara to Oneonta (New York) | 3,982.09 mi (6,408.56 km) |
| Mortara to Ontario (California) | 6,013.64 mi (9,678.01 km) |
| Mortara to Ontario (Oregon) | 5,429.39 mi (8,737.76 km) |
| Mortara to Opa-locka (Florida) | 4,923.89 mi (7,924.23 km) |
| Mortara to Opelika (Alabama) | 4,842.46 mi (7,793.19 km) |
| Mortara to Opelousas (Louisiana) | 5,231.38 mi (8,419.09 km) |
| Mortara to Orange (California) | 6,034.04 mi (9,710.85 km) |
| Mortara to Orange (Texas) | 5,322.02 mi (8,564.97 km) |
| Mortara to Orange City (Florida) | 4,831.61 mi (7,775.73 km) |
| Mortara to Orangeburg (South Carolina) | 4,607.31 mi (7,414.75 km) |
