| Diamond Bar to Olympia Heights (Florida) | 2,303.55 mi (3,707.20 km) |
| Diamond Bar to Omaha (Nebraska) | 1,287.76 mi (2,072.45 km) |
| Diamond Bar to On Top of the World Designated Place (Florida) | 2,108.42 mi (3,393.17 km) |
| Diamond Bar to Onalaska (Wisconsin) | 1,575.36 mi (2,535.29 km) |
| Diamond Bar to Oneida (New York) | 2,336.36 mi (3,760.01 km) |
| Diamond Bar to Oneonta (New York) | 2,366.20 mi (3,808.03 km) |
| Diamond Bar to Ontario (California) | 12.32 mi (19.83 km) |
| Diamond Bar to Ontario (Oregon) | 694.23 mi (1,117.26 km) |
| Diamond Bar to Opa-locka (Florida) | 2,303.53 mi (3,707.18 km) |
| Diamond Bar to Opelika (Alabama) | 1,867.15 mi (3,004.89 km) |
| Diamond Bar to Opelousas (Louisiana) | 1,518.50 mi (2,443.79 km) |
| Diamond Bar to Orange (California) | 13.50 mi (21.73 km) |
| Diamond Bar to Orange (Texas) | 1,430.34 mi (2,301.91 km) |
| Diamond Bar to Orange City (Florida) | 2,169.37 mi (3,491.26 km) |
| Diamond Bar to Orangeburg (South Carolina) | 2,111.39 mi (3,397.95 km) |
