| Castelli Calepio to Olympia Heights (Florida) | 4,980.37 mi (8,015.14 km) |
| Castelli Calepio to Omaha (Nebraska) | 4,899.60 mi (7,885.15 km) |
| Castelli Calepio to On Top of the World Designated Place (Florida) | 4,910.41 mi (7,902.55 km) |
| Castelli Calepio to Onalaska (Wisconsin) | 4,595.74 mi (7,396.13 km) |
| Castelli Calepio to Oneida (New York) | 4,017.44 mi (6,465.45 km) |
| Castelli Calepio to Oneonta (New York) | 4,017.22 mi (6,465.09 km) |
| Castelli Calepio to Ontario (California) | 6,030.79 mi (9,705.62 km) |
| Castelli Calepio to Ontario (Oregon) | 5,440.98 mi (8,756.41 km) |
| Castelli Calepio to Opa-locka (Florida) | 4,968.32 mi (7,995.73 km) |
| Castelli Calepio to Opelika (Alabama) | 4,880.10 mi (7,853.76 km) |
| Castelli Calepio to Opelousas (Louisiana) | 5,266.86 mi (8,476.19 km) |
| Castelli Calepio to Orange (California) | 6,051.18 mi (9,738.43 km) |
| Castelli Calepio to Orange (Texas) | 5,356.83 mi (8,620.98 km) |
| Castelli Calepio to Orange City (Florida) | 4,873.71 mi (7,843.48 km) |
| Castelli Calepio to Orangeburg (South Carolina) | 4,646.63 mi (7,478.03 km) |
