| Duncan to Oswego (Illinois) | 716.78 mi (1,153.55 km) |
| Duncan to Oswego (New York) | 1,299.28 mi (2,090.98 km) |
| Duncan to Otsego (Minnesota) | 775.01 mi (1,247.25 km) |
| Duncan to Ottawa (Illinois) | 682.84 mi (1,098.92 km) |
| Duncan to Ottawa (Kansas) | 316.81 mi (509.86 km) |
| Duncan to Ottumwa (Iowa) | 538.87 mi (867.24 km) |
| Duncan to Overland (Missouri) | 507.52 mi (816.78 km) |
| Duncan to Overland Park (Kansas) | 349.61 mi (562.64 km) |
| Duncan to Overlea (Maryland) | 1,224.59 mi (1,970.79 km) |
| Duncan to Oviedo (Florida) | 1,063.63 mi (1,711.75 km) |
| Duncan to Owasso (Oklahoma) | 168.59 mi (271.32 km) |
| Duncan to Owatonna (Minnesota) | 705.57 mi (1,135.51 km) |
| Duncan to Owensboro (Kentucky) | 641.97 mi (1,033.16 km) |
| Duncan to Owings Mills (Maryland) | 1,210.69 mi (1,948.41 km) |
| Duncan to Owosso (Michigan) | 941.07 mi (1,514.50 km) |
