| Prospect Heights to Odenton (Maryland) | 625.09 mi (1,005.98 km) |
| Prospect Heights to Odessa (Texas) | 1,061.29 mi (1,707.98 km) |
| Prospect Heights to Ogden (Utah) | 1,238.28 mi (1,992.82 km) |
| Prospect Heights to Oildale (California) | 1,727.33 mi (2,779.88 km) |
| Prospect Heights to Ojus (Florida) | 1,199.71 mi (1,930.75 km) |
| Prospect Heights to Okemos (Michigan) | 183.98 mi (296.09 km) |
| Prospect Heights to Oklahoma City (Oklahoma) | 689.72 mi (1,110.00 km) |
| Prospect Heights to Okmulgee (Oklahoma) | 624.00 mi (1,004.23 km) |
| Prospect Heights to Olathe (Kansas) | 424.89 mi (683.79 km) |
| Prospect Heights to Old Jamestown (Missouri) | 257.34 mi (414.14 km) |
| Prospect Heights to Oldsmar (Florida) | 1,014.92 mi (1,633.35 km) |
| Prospect Heights to Olean (New York) | 486.55 mi (783.03 km) |
| Prospect Heights to Olive Branch (Mississippi) | 504.28 mi (811.56 km) |
| Prospect Heights to Olivehurst (California) | 1,765.30 mi (2,840.97 km) |
| Prospect Heights to Olney (Maryland) | 604.29 mi (972.51 km) |
