| Boulder to Smyrna (Delaware) | 1,570.33 mi (2,527.21 km) |
| Boulder to Smyrna (Georgia) | 1,218.09 mi (1,960.32 km) |
| Boulder to Smyrna (Tennessee) | 1,055.17 mi (1,698.13 km) |
| Boulder to Snellville (Georgia) | 1,244.69 mi (2,003.13 km) |
| Boulder to Snoqualmie (Washington) | 973.53 mi (1,566.75 km) |
| Boulder to Snyder (Texas) | 559.74 mi (900.81 km) |
| Boulder to Socastee (South Carolina) | 1,509.19 mi (2,428.80 km) |
| Boulder to Socorro (Texas) | 582.18 mi (936.93 km) |
| Boulder to Soddy-Daisy (Tennessee) | 1,143.99 mi (1,841.07 km) |
| Boulder to Solana Beach (California) | 823.64 mi (1,325.52 km) |
| Boulder to Soledad (California) | 906.18 mi (1,458.36 km) |
| Boulder to Solon (Ohio) | 1,246.84 mi (2,006.60 km) |
| Boulder to Somers Point (New Jersey) | 1,622.50 mi (2,611.16 km) |
| Boulder to Somerset (Kentucky) | 1,131.00 mi (1,820.17 km) |
| Boulder to Somerset (New Jersey) | 1,613.33 mi (2,596.41 km) |
