| Rockville to Orangeburg (South Carolina) | 438.00 mi (704.90 km) |
| Rockville to Orangevale (California) | 2,346.29 mi (3,776.00 km) |
| Rockville to Orchards (Washington) | 2,327.94 mi (3,746.46 km) |
| Rockville to Orcutt (California) | 2,383.37 mi (3,835.66 km) |
| Rockville to Oregon (Ohio) | 374.94 mi (603.41 km) |
| Rockville to Oregon (Wisconsin) | 690.08 mi (1,110.58 km) |
| Rockville to Oregon City (Oregon) | 2,333.21 mi (3,754.94 km) |
| Rockville to Orem (Utah) | 1,826.87 mi (2,940.07 km) |
| Rockville to Orinda (California) | 2,411.34 mi (3,880.68 km) |
| Rockville to Orland Park (Illinois) | 589.70 mi (949.03 km) |
| Rockville to Orlando (Florida) | 770.90 mi (1,240.65 km) |
| Rockville to Ormond Beach (Florida) | 712.48 mi (1,146.63 km) |
| Rockville to Oro Valley (Arizona) | 1,939.52 mi (3,121.36 km) |
| Rockville to Oroville (California) | 2,350.18 mi (3,782.25 km) |
| Rockville to Oshkosh (Wisconsin) | 680.50 mi (1,095.16 km) |
