| Duncan to Castle Pines (Colorado) | 512.21 mi (824.32 km) |
| Duncan to Castle Rock (Colorado) | 507.74 mi (817.12 km) |
| Duncan to Castro Valley (California) | 1,361.06 mi (2,190.41 km) |
| Duncan to Catalina Foothills (Arizona) | 762.72 mi (1,227.48 km) |
| Duncan to Cataño (Puerto Rico) | 2,243.81 mi (3,611.07 km) |
| Duncan to Cathedral City (California) | 1,059.41 mi (1,704.96 km) |
| Duncan to Catonsville (Maryland) | 1,211.63 mi (1,949.94 km) |
| Duncan to Cave Spring (Virginia) | 1,018.24 mi (1,638.70 km) |
| Duncan to Cayce (South Carolina) | 963.80 mi (1,551.09 km) |
| Duncan to Cayey (Puerto Rico) | 2,256.00 mi (3,630.69 km) |
| Duncan to Cedar City (Utah) | 873.27 mi (1,405.40 km) |
| Duncan to Cedar Falls (Iowa) | 625.15 mi (1,006.08 km) |
| Duncan to Cedar Hill (Texas) | 146.31 mi (235.46 km) |
| Duncan to Cedar Lake (Indiana) | 739.81 mi (1,190.61 km) |
| Duncan to Cedar Mill (Oregon) | 1,510.36 mi (2,430.68 km) |
