| Gateway to Olympia Heights (Florida) | 105.33 mi (169.51 km) |
| Gateway to Omaha (Nebraska) | 1,300.93 mi (2,093.65 km) |
| Gateway to On Top of the World Designated Place (Florida) | 177.68 mi (285.94 km) |
| Gateway to Onalaska (Wisconsin) | 1,307.60 mi (2,104.37 km) |
| Gateway to Oneida (New York) | 1,190.07 mi (1,915.23 km) |
| Gateway to Oneonta (New York) | 1,159.94 mi (1,866.74 km) |
| Gateway to Ontario (California) | 2,188.45 mi (3,521.97 km) |
| Gateway to Ontario (Oregon) | 2,297.89 mi (3,698.10 km) |
| Gateway to Opa-locka (Florida) | 103.56 mi (166.67 km) |
| Gateway to Opelika (Alabama) | 473.38 mi (761.83 km) |
| Gateway to Opelousas (Louisiana) | 683.64 mi (1,100.22 km) |
| Gateway to Orange (California) | 2,199.76 mi (3,540.18 km) |
| Gateway to Orange (Texas) | 770.08 mi (1,239.32 km) |
| Gateway to Orange City (Florida) | 165.12 mi (265.74 km) |
| Gateway to Orangeburg (South Carolina) | 480.54 mi (773.36 km) |
