| Potomac to Oskaloosa (Iowa) | 829.57 mi (1,335.07 km) |
| Potomac to Oswego (Illinois) | 614.53 mi (988.98 km) |
| Potomac to Oswego (New York) | 308.71 mi (496.82 km) |
| Potomac to Otsego (Minnesota) | 943.49 mi (1,518.40 km) |
| Potomac to Ottawa (Illinois) | 634.38 mi (1,020.94 km) |
| Potomac to Ottawa (Kansas) | 971.71 mi (1,563.81 km) |
| Potomac to Ottumwa (Iowa) | 816.33 mi (1,313.76 km) |
| Potomac to Overland (Missouri) | 708.58 mi (1,140.35 km) |
| Potomac to Overland Park (Kansas) | 938.53 mi (1,510.41 km) |
| Potomac to Overlea (Maryland) | 43.57 mi (70.13 km) |
| Potomac to Oviedo (Florida) | 751.11 mi (1,208.79 km) |
| Potomac to Owasso (Oklahoma) | 1,034.85 mi (1,665.43 km) |
| Potomac to Owatonna (Minnesota) | 898.41 mi (1,445.85 km) |
| Potomac to Owensboro (Kentucky) | 544.09 mi (875.63 km) |
| Potomac to Owings Mills (Maryland) | 34.92 mi (56.20 km) |
