| Rockville to Oskaloosa (Iowa) | 830.29 mi (1,336.23 km) |
| Rockville to Oswego (Illinois) | 614.78 mi (989.40 km) |
| Rockville to Oswego (New York) | 303.72 mi (488.79 km) |
| Rockville to Otsego (Minnesota) | 942.69 mi (1,517.11 km) |
| Rockville to Ottawa (Illinois) | 634.87 mi (1,021.73 km) |
| Rockville to Ottawa (Kansas) | 973.47 mi (1,566.65 km) |
| Rockville to Ottumwa (Iowa) | 817.17 mi (1,315.10 km) |
| Rockville to Overland (Missouri) | 710.49 mi (1,143.42 km) |
| Rockville to Overland Park (Kansas) | 940.21 mi (1,513.12 km) |
| Rockville to Overlea (Maryland) | 39.27 mi (63.19 km) |
| Rockville to Oviedo (Florida) | 756.32 mi (1,217.17 km) |
| Rockville to Owasso (Oklahoma) | 1,037.33 mi (1,669.42 km) |
| Rockville to Owatonna (Minnesota) | 898.01 mi (1,445.21 km) |
| Rockville to Owensboro (Kentucky) | 546.70 mi (879.82 km) |
| Rockville to Owings Mills (Maryland) | 29.89 mi (48.10 km) |
