| Duncan to Orangevale (California) | 1,319.69 mi (2,123.84 km) |
| Duncan to Orchards (Washington) | 1,502.18 mi (2,417.53 km) |
| Duncan to Orcutt (California) | 1,275.58 mi (2,052.84 km) |
| Duncan to Oregon (Ohio) | 926.62 mi (1,491.25 km) |
| Duncan to Oregon (Wisconsin) | 738.80 mi (1,188.98 km) |
| Duncan to Oregon City (Oregon) | 1,496.08 mi (2,407.71 km) |
| Duncan to Orem (Utah) | 852.94 mi (1,372.68 km) |
| Duncan to Orinda (California) | 1,367.85 mi (2,201.34 km) |
| Duncan to Orland Park (Illinois) | 732.40 mi (1,178.68 km) |
| Duncan to Orlando (Florida) | 1,061.21 mi (1,707.86 km) |
| Duncan to Ormond Beach (Florida) | 1,049.19 mi (1,688.51 km) |
| Duncan to Oro Valley (Arizona) | 765.90 mi (1,232.59 km) |
| Duncan to Oroville (California) | 1,344.13 mi (2,163.17 km) |
| Duncan to Oshkosh (Wisconsin) | 823.30 mi (1,324.97 km) |
| Duncan to Oskaloosa (Iowa) | 547.88 mi (881.73 km) |
