| Keystone to Olympia Heights (Florida) | 216.93 mi (349.11 km) |
| Keystone to Omaha (Nebraska) | 1,183.26 mi (1,904.27 km) |
| Keystone to On Top of the World Designated Place (Florida) | 69.97 mi (112.60 km) |
| Keystone to Onalaska (Wisconsin) | 1,188.61 mi (1,912.88 km) |
| Keystone to Oneida (New York) | 1,102.72 mi (1,774.66 km) |
| Keystone to Oneonta (New York) | 1,075.88 mi (1,731.46 km) |
| Keystone to Ontario (California) | 2,100.67 mi (3,380.71 km) |
| Keystone to Ontario (Oregon) | 2,188.66 mi (3,522.31 km) |
| Keystone to Opa-locka (Florida) | 211.18 mi (339.87 km) |
| Keystone to Opelika (Alabama) | 354.01 mi (569.73 km) |
| Keystone to Opelousas (Louisiana) | 594.40 mi (956.59 km) |
| Keystone to Orange (California) | 2,112.66 mi (3,399.99 km) |
| Keystone to Orange (Texas) | 687.22 mi (1,105.97 km) |
| Keystone to Orange City (Florida) | 97.07 mi (156.22 km) |
| Keystone to Orangeburg (South Carolina) | 384.44 mi (618.69 km) |
