| Galveston to Olympia Heights (Florida) | 923.88 mi (1,486.85 km) |
| Galveston to Omaha (Nebraska) | 832.67 mi (1,340.05 km) |
| Galveston to On Top of the World Designated Place (Florida) | 760.10 mi (1,223.26 km) |
| Galveston to Onalaska (Wisconsin) | 1,031.67 mi (1,660.32 km) |
| Galveston to Oneida (New York) | 1,430.06 mi (2,301.46 km) |
| Galveston to Oneonta (New York) | 1,430.72 mi (2,302.52 km) |
| Galveston to Ontario (California) | 1,373.34 mi (2,210.18 km) |
| Galveston to Ontario (Oregon) | 1,585.20 mi (2,551.13 km) |
| Galveston to Opa-locka (Florida) | 925.04 mi (1,488.71 km) |
| Galveston to Opelika (Alabama) | 610.76 mi (982.93 km) |
| Galveston to Opelousas (Louisiana) | 190.02 mi (305.81 km) |
| Galveston to Orange (California) | 1,383.52 mi (2,226.57 km) |
| Galveston to Orange (Texas) | 90.85 mi (146.21 km) |
| Galveston to Orange City (Florida) | 821.14 mi (1,321.50 km) |
| Galveston to Orangeburg (South Carolina) | 876.86 mi (1,411.17 km) |
