| Boulder to Superior (Colorado) | 7.99 mi (12.87 km) |
| Boulder to Superior (Wisconsin) | 804.57 mi (1,294.82 km) |
| Boulder to Surprise (Arizona) | 591.60 mi (952.09 km) |
| Boulder to Susanville (California) | 809.81 mi (1,303.26 km) |
| Boulder to Sussex (Wisconsin) | 904.27 mi (1,455.28 km) |
| Boulder to Suwanee (Georgia) | 1,235.47 mi (1,988.29 km) |
| Boulder to Swansea (Illinois) | 821.70 mi (1,322.40 km) |
| Boulder to Sweetwater (Florida) | 1,737.05 mi (2,795.51 km) |
| Boulder to Sweetwater (Texas) | 587.42 mi (945.37 km) |
| Boulder to Sycamore (Illinois) | 873.17 mi (1,405.24 km) |
| Boulder to Sylacauga (Alabama) | 1,151.70 mi (1,853.47 km) |
| Boulder to Sylvania (Ohio) | 1,128.67 mi (1,816.41 km) |
| Boulder to Syosset (New York) | 1,661.84 mi (2,674.47 km) |
| Boulder to Syracuse (New York) | 1,512.18 mi (2,433.62 km) |
| Boulder to Syracuse (Utah) | 365.21 mi (587.75 km) |
