| Humble to Olympia Heights (Florida) | 957.41 mi (1,540.80 km) |
| Humble to Omaha (Nebraska) | 779.97 mi (1,255.24 km) |
| Humble to On Top of the World Designated Place (Florida) | 782.10 mi (1,258.66 km) |
| Humble to Onalaska (Wisconsin) | 985.60 mi (1,586.17 km) |
| Humble to Oneida (New York) | 1,408.53 mi (2,266.81 km) |
| Humble to Oneonta (New York) | 1,411.16 mi (2,271.04 km) |
| Humble to Ontario (California) | 1,335.48 mi (2,149.25 km) |
| Humble to Ontario (Oregon) | 1,532.74 mi (2,466.71 km) |
| Humble to Opa-locka (Florida) | 957.92 mi (1,541.63 km) |
| Humble to Opelika (Alabama) | 611.78 mi (984.57 km) |
| Humble to Opelousas (Louisiana) | 193.54 mi (311.48 km) |
| Humble to Orange (California) | 1,346.21 mi (2,166.52 km) |
| Humble to Orange (Texas) | 90.44 mi (145.55 km) |
| Humble to Orange City (Florida) | 843.48 mi (1,357.46 km) |
| Humble to Orangeburg (South Carolina) | 879.06 mi (1,414.70 km) |
