| Rockville to Odenton (Maryland) | 24.78 mi (39.88 km) |
| Rockville to Odessa (Texas) | 1,496.17 mi (2,407.86 km) |
| Rockville to Ogden (Utah) | 1,832.06 mi (2,948.41 km) |
| Rockville to Oildale (California) | 2,296.33 mi (3,695.59 km) |
| Rockville to Ojus (Florida) | 923.58 mi (1,486.35 km) |
| Rockville to Okemos (Michigan) | 453.99 mi (730.63 km) |
| Rockville to Oklahoma City (Oklahoma) | 1,144.22 mi (1,841.44 km) |
| Rockville to Okmulgee (Oklahoma) | 1,060.73 mi (1,707.08 km) |
| Rockville to Olathe (Kansas) | 947.34 mi (1,524.60 km) |
| Rockville to Old Jamestown (Missouri) | 704.96 mi (1,134.53 km) |
| Rockville to Oldsmar (Florida) | 825.31 mi (1,328.20 km) |
| Rockville to Olean (New York) | 217.73 mi (350.41 km) |
| Rockville to Olive Branch (Mississippi) | 754.98 mi (1,215.03 km) |
| Rockville to Olivehurst (California) | 2,356.92 mi (3,793.10 km) |
| Rockville to Olney (Maryland) | 6.26 mi (10.07 km) |
