| Duncan to Odessa (Texas) | 314.87 mi (506.73 km) |
| Duncan to Ogden (Utah) | 892.88 mi (1,436.95 km) |
| Duncan to Oildale (California) | 1,194.26 mi (1,921.97 km) |
| Duncan to Ojus (Florida) | 1,212.03 mi (1,950.57 km) |
| Duncan to Okemos (Michigan) | 919.97 mi (1,480.55 km) |
| Duncan to Oklahoma City (Oklahoma) | 68.07 mi (109.55 km) |
| Duncan to Okmulgee (Oklahoma) | 131.20 mi (211.14 km) |
| Duncan to Olathe (Kansas) | 345.68 mi (556.32 km) |
| Duncan to Old Jamestown (Missouri) | 516.64 mi (831.45 km) |
| Duncan to Oldsmar (Florida) | 1,004.39 mi (1,616.40 km) |
| Duncan to Olean (New York) | 1,174.35 mi (1,889.93 km) |
| Duncan to Olive Branch (Mississippi) | 459.19 mi (738.99 km) |
| Duncan to Olivehurst (California) | 1,340.36 mi (2,157.10 km) |
| Duncan to Olney (Maryland) | 1,192.96 mi (1,919.88 km) |
| Duncan to Olympia (Washington) | 1,555.37 mi (2,503.12 km) |
