| Duncan to Oakley (California) | 1,341.87 mi (2,159.52 km) |
| Duncan to Oakton (Virginia) | 1,178.06 mi (1,895.91 km) |
| Duncan to Oakville (Missouri) | 500.88 mi (806.09 km) |
| Duncan to Oatfield (Oregon) | 1,497.93 mi (2,410.69 km) |
| Duncan to Ocala (Florida) | 995.45 mi (1,602.03 km) |
| Duncan to Ocean Acres (New Jersey) | 1,346.32 mi (2,166.70 km) |
| Duncan to Ocean City (New Jersey) | 1,325.05 mi (2,132.47 km) |
| Duncan to Ocean Pines (Maryland) | 1,289.49 mi (2,075.23 km) |
| Duncan to Ocean Pointe (Hawaii) | 3,727.35 mi (5,998.60 km) |
| Duncan to Ocean Springs (Mississippi) | 603.85 mi (971.80 km) |
| Duncan to Oceanside (California) | 1,114.02 mi (1,792.85 km) |
| Duncan to Oceanside (New York) | 1,389.45 mi (2,236.10 km) |
| Duncan to Ocoee (Florida) | 1,047.39 mi (1,685.61 km) |
| Duncan to Oconomowoc (Wisconsin) | 778.19 mi (1,252.37 km) |
| Duncan to Odenton (Maryland) | 1,212.14 mi (1,950.75 km) |
