| Herndon to Oswego (Illinois) | 606.00 mi (975.27 km) |
| Herndon to Oswego (New York) | 313.06 mi (503.82 km) |
| Herndon to Otsego (Minnesota) | 936.45 mi (1,507.07 km) |
| Herndon to Ottawa (Illinois) | 625.58 mi (1,006.77 km) |
| Herndon to Ottawa (Kansas) | 961.62 mi (1,547.58 km) |
| Herndon to Ottumwa (Iowa) | 807.12 mi (1,298.93 km) |
| Herndon to Overland (Missouri) | 698.39 mi (1,123.95 km) |
| Herndon to Overland Park (Kansas) | 928.50 mi (1,494.28 km) |
| Herndon to Overlea (Maryland) | 53.95 mi (86.82 km) |
| Herndon to Oviedo (Florida) | 744.93 mi (1,198.85 km) |
| Herndon to Owasso (Oklahoma) | 1,024.30 mi (1,648.45 km) |
| Herndon to Owatonna (Minnesota) | 890.76 mi (1,433.54 km) |
| Herndon to Owensboro (Kentucky) | 533.50 mi (858.58 km) |
| Herndon to Owings Mills (Maryland) | 44.13 mi (71.02 km) |
| Herndon to Owosso (Michigan) | 450.04 mi (724.27 km) |
