| Darby to Olympia Heights (Florida) | 1,023.77 mi (1,647.60 km) |
| Darby to Omaha (Nebraska) | 1,092.20 mi (1,757.72 km) |
| Darby to On Top of the World Designated Place (Florida) | 846.86 mi (1,362.88 km) |
| Darby to Onalaska (Wisconsin) | 862.97 mi (1,388.81 km) |
| Darby to Oneida (New York) | 219.04 mi (352.51 km) |
| Darby to Oneonta (New York) | 175.38 mi (282.25 km) |
| Darby to Ontario (California) | 2,349.95 mi (3,781.89 km) |
| Darby to Ontario (Oregon) | 2,138.38 mi (3,441.39 km) |
| Darby to Opa-locka (Florida) | 1,010.68 mi (1,626.54 km) |
| Darby to Opelika (Alabama) | 753.38 mi (1,212.45 km) |
| Darby to Opelousas (Louisiana) | 1,147.00 mi (1,845.91 km) |
| Darby to Orange (California) | 2,367.63 mi (3,810.33 km) |
| Darby to Orange (Texas) | 1,242.69 mi (1,999.91 km) |
| Darby to Orange City (Florida) | 832.63 mi (1,339.98 km) |
| Darby to Orangeburg (South Carolina) | 541.66 mi (871.72 km) |
