| Prospect Heights to Orangeburg (South Carolina) | 708.30 mi (1,139.89 km) |
| Prospect Heights to Orangevale (California) | 1,756.51 mi (2,826.83 km) |
| Prospect Heights to Orchards (Washington) | 1,726.86 mi (2,779.11 km) |
| Prospect Heights to Orcutt (California) | 1,814.95 mi (2,920.88 km) |
| Prospect Heights to Oregon (Ohio) | 233.29 mi (375.44 km) |
| Prospect Heights to Oregon (Wisconsin) | 93.64 mi (150.70 km) |
| Prospect Heights to Oregon City (Oregon) | 1,731.78 mi (2,787.04 km) |
| Prospect Heights to Orem (Utah) | 1,238.10 mi (1,992.53 km) |
| Prospect Heights to Orinda (California) | 1,823.96 mi (2,935.39 km) |
| Prospect Heights to Orland Park (Illinois) | 34.46 mi (55.46 km) |
| Prospect Heights to Orlando (Florida) | 1,011.37 mi (1,627.64 km) |
| Prospect Heights to Ormond Beach (Florida) | 963.25 mi (1,550.20 km) |
| Prospect Heights to Oro Valley (Arizona) | 1,426.77 mi (2,296.17 km) |
| Prospect Heights to Oroville (California) | 1,757.02 mi (2,827.65 km) |
| Prospect Heights to Oshkosh (Wisconsin) | 136.40 mi (219.51 km) |
