| Prospect Heights to Olympia (Washington) | 1,739.47 mi (2,799.41 km) |
| Prospect Heights to Olympia Heights (Florida) | 1,211.20 mi (1,949.23 km) |
| Prospect Heights to Omaha (Nebraska) | 423.16 mi (681.01 km) |
| Prospect Heights to On Top of the World Designated Place (Florida) | 951.74 mi (1,531.68 km) |
| Prospect Heights to Onalaska (Wisconsin) | 206.58 mi (332.46 km) |
| Prospect Heights to Oneida (New York) | 626.90 mi (1,008.90 km) |
| Prospect Heights to Oneonta (New York) | 657.23 mi (1,057.71 km) |
| Prospect Heights to Ontario (California) | 1,697.63 mi (2,732.08 km) |
| Prospect Heights to Ontario (Oregon) | 1,464.73 mi (2,357.25 km) |
| Prospect Heights to Opa-locka (Florida) | 1,201.44 mi (1,933.53 km) |
| Prospect Heights to Opelika (Alabama) | 667.18 mi (1,073.73 km) |
| Prospect Heights to Opelousas (Louisiana) | 832.49 mi (1,339.76 km) |
| Prospect Heights to Orange (California) | 1,716.20 mi (2,761.95 km) |
| Prospect Heights to Orange (Texas) | 888.99 mi (1,430.69 km) |
| Prospect Heights to Orange City (Florida) | 982.69 mi (1,581.49 km) |
