| Herndon to Olympia Heights (Florida) | 931.13 mi (1,498.50 km) |
| Herndon to Omaha (Nebraska) | 996.93 mi (1,604.40 km) |
| Herndon to On Top of the World Designated Place (Florida) | 736.70 mi (1,185.61 km) |
| Herndon to Onalaska (Wisconsin) | 791.18 mi (1,273.28 km) |
| Herndon to Oneida (New York) | 297.64 mi (479.01 km) |
| Herndon to Oneonta (New York) | 269.69 mi (434.03 km) |
| Herndon to Ontario (California) | 2,241.19 mi (3,606.85 km) |
| Herndon to Ontario (Oregon) | 2,058.02 mi (3,312.06 km) |
| Herndon to Opa-locka (Florida) | 918.28 mi (1,477.82 km) |
| Herndon to Opelika (Alabama) | 624.33 mi (1,004.75 km) |
| Herndon to Opelousas (Louisiana) | 1,015.92 mi (1,634.97 km) |
| Herndon to Orange (California) | 2,258.51 mi (3,634.73 km) |
| Herndon to Orange (Texas) | 1,111.72 mi (1,789.13 km) |
| Herndon to Orange City (Florida) | 728.31 mi (1,172.10 km) |
| Herndon to Orangeburg (South Carolina) | 425.16 mi (684.22 km) |
