| Cal to Olympia Heights (Florida) | 6,106.57 mi (9,827.58 km) |
| Cal to Omaha (Nebraska) | 5,966.38 mi (9,601.97 km) |
| Cal to On Top of the World Designated Place (Florida) | 6,036.58 mi (9,714.94 km) |
| Cal to Onalaska (Wisconsin) | 5,667.18 mi (9,120.44 km) |
| Cal to Oneida (New York) | 5,128.40 mi (8,253.36 km) |
| Cal to Oneonta (New York) | 5,130.80 mi (8,257.23 km) |
| Cal to Ontario (California) | 7,022.73 mi (11,301.99 km) |
| Cal to Ontario (Oregon) | 6,387.03 mi (10,278.93 km) |
| Cal to Opa-locka (Florida) | 6,094.57 mi (9,808.26 km) |
| Cal to Opelika (Alabama) | 5,999.85 mi (9,655.82 km) |
| Cal to Opelousas (Louisiana) | 6,379.88 mi (10,267.43 km) |
| Cal to Orange (California) | 7,042.76 mi (11,334.23 km) |
| Cal to Orange (Texas) | 6,467.33 mi (10,408.16 km) |
| Cal to Orange City (Florida) | 6,000.26 mi (9,656.49 km) |
| Cal to Orangeburg (South Carolina) | 5,770.07 mi (9,286.03 km) |
