| Havre de Grace to Olympia Heights (Florida) | 985.93 mi (1,586.69 km) |
| Havre de Grace to Omaha (Nebraska) | 1,053.34 mi (1,695.18 km) |
| Havre de Grace to On Top of the World Designated Place (Florida) | 802.31 mi (1,291.20 km) |
| Havre de Grace to Onalaska (Wisconsin) | 832.64 mi (1,340.00 km) |
| Havre de Grace to Oneida (New York) | 244.95 mi (394.21 km) |
| Havre de Grace to Oneonta (New York) | 208.16 mi (335.00 km) |
| Havre de Grace to Ontario (California) | 2,306.38 mi (3,711.77 km) |
| Havre de Grace to Ontario (Oregon) | 2,105.79 mi (3,388.94 km) |
| Havre de Grace to Opa-locka (Florida) | 972.91 mi (1,565.75 km) |
| Havre de Grace to Opelika (Alabama) | 701.94 mi (1,129.66 km) |
| Havre de Grace to Opelousas (Louisiana) | 1,094.83 mi (1,761.96 km) |
| Havre de Grace to Orange (California) | 2,323.93 mi (3,740.00 km) |
| Havre de Grace to Orange (Texas) | 1,190.56 mi (1,916.02 km) |
| Havre de Grace to Orange City (Florida) | 790.21 mi (1,271.72 km) |
| Havre de Grace to Orangeburg (South Carolina) | 494.46 mi (795.75 km) |
