| Prospect Heights to Oskaloosa (Iowa) | 249.52 mi (401.57 km) |
| Prospect Heights to Oswego (Illinois) | 35.91 mi (57.80 km) |
| Prospect Heights to Oswego (New York) | 586.42 mi (943.75 km) |
| Prospect Heights to Otsego (Minnesota) | 358.54 mi (577.01 km) |
| Prospect Heights to Ottawa (Illinois) | 69.46 mi (111.78 km) |
| Prospect Heights to Ottawa (Kansas) | 455.67 mi (733.33 km) |
| Prospect Heights to Ottumwa (Iowa) | 243.98 mi (392.64 km) |
| Prospect Heights to Overland (Missouri) | 268.18 mi (431.59 km) |
| Prospect Heights to Overland Park (Kansas) | 418.81 mi (674.01 km) |
| Prospect Heights to Overlea (Maryland) | 626.03 mi (1,007.50 km) |
| Prospect Heights to Oviedo (Florida) | 1,002.74 mi (1,613.76 km) |
| Prospect Heights to Owasso (Oklahoma) | 583.14 mi (938.48 km) |
| Prospect Heights to Owatonna (Minnesota) | 300.71 mi (483.94 km) |
| Prospect Heights to Owensboro (Kentucky) | 303.35 mi (488.19 km) |
| Prospect Heights to Owings Mills (Maryland) | 611.22 mi (983.66 km) |
