| Boulder to Southern Pines (North Carolina) | 1,448.15 mi (2,330.57 km) |
| Boulder to Southfield (Michigan) | 1,151.57 mi (1,853.27 km) |
| Boulder to Southgate (Michigan) | 1,154.19 mi (1,857.48 km) |
| Boulder to Southlake (Texas) | 663.62 mi (1,068.00 km) |
| Boulder to Spanaway (Washington) | 985.80 mi (1,586.49 km) |
| Boulder to Spanish Fork (Utah) | 337.76 mi (543.57 km) |
| Boulder to Spanish Lake (Missouri) | 806.73 mi (1,298.30 km) |
| Boulder to Spanish Springs (Nevada) | 764.43 mi (1,230.24 km) |
| Boulder to Sparks (Nevada) | 767.58 mi (1,235.30 km) |
| Boulder to Spartanburg (South Carolina) | 1,321.95 mi (2,127.48 km) |
| Boulder to Spearfish (South Dakota) | 317.19 mi (510.47 km) |
| Boulder to Speedway (Indiana) | 1,005.42 mi (1,618.06 km) |
| Boulder to Spencer (Iowa) | 564.25 mi (908.08 km) |
| Boulder to Spokane (Washington) | 802.81 mi (1,291.99 km) |
| Boulder to Spokane Valley (Washington) | 795.24 mi (1,279.81 km) |
