| Gary to Oswego (Illinois) | 51.52 mi (82.91 km) |
| Gary to Oswego (New York) | 566.68 mi (911.98 km) |
| Gary to Otsego (Minnesota) | 404.22 mi (650.52 km) |
| Gary to Ottawa (Illinois) | 78.26 mi (125.94 km) |
| Gary to Ottawa (Kansas) | 466.41 mi (750.61 km) |
| Gary to Ottumwa (Iowa) | 266.12 mi (428.27 km) |
| Gary to Overland (Missouri) | 255.79 mi (411.66 km) |
| Gary to Overland Park (Kansas) | 429.63 mi (691.42 km) |
| Gary to Overlea (Maryland) | 589.14 mi (948.13 km) |
| Gary to Oviedo (Florida) | 958.28 mi (1,542.20 km) |
| Gary to Owasso (Oklahoma) | 584.40 mi (940.50 km) |
| Gary to Owatonna (Minnesota) | 344.42 mi (554.29 km) |
| Gary to Owensboro (Kentucky) | 265.12 mi (426.66 km) |
| Gary to Owings Mills (Maryland) | 574.24 mi (924.15 km) |
| Gary to Owosso (Michigan) | 188.91 mi (304.02 km) |
