| Boulder to Castle Rock (Colorado) | 49.57 mi (79.78 km) |
| Boulder to Castro Valley (California) | 916.94 mi (1,475.67 km) |
| Boulder to Catalina Foothills (Arizona) | 618.70 mi (995.70 km) |
| Boulder to Cataño (Puerto Rico) | 2,757.24 mi (4,437.35 km) |
| Boulder to Cathedral City (California) | 751.56 mi (1,209.52 km) |
| Boulder to Catonsville (Maryland) | 1,511.24 mi (2,432.10 km) |
| Boulder to Cave Spring (Virginia) | 1,371.68 mi (2,207.50 km) |
| Boulder to Cayce (South Carolina) | 1,395.51 mi (2,245.86 km) |
| Boulder to Cayey (Puerto Rico) | 2,771.01 mi (4,459.51 km) |
| Boulder to Cedar City (Utah) | 451.76 mi (727.03 km) |
| Boulder to Cedar Falls (Iowa) | 685.87 mi (1,103.80 km) |
| Boulder to Cedar Hill (Texas) | 690.55 mi (1,111.33 km) |
| Boulder to Cedar Lake (Indiana) | 936.09 mi (1,506.50 km) |
| Boulder to Cedar Mill (Oregon) | 965.33 mi (1,553.55 km) |
| Boulder to Cedar Park (Texas) | 779.01 mi (1,253.69 km) |
