| Boulder to Silver Firs (Washington) | 996.65 mi (1,603.95 km) |
| Boulder to Silver Spring (Maryland) | 1,500.21 mi (2,414.35 km) |
| Boulder to Silver Springs Shores (Florida) | 1,515.17 mi (2,438.43 km) |
| Boulder to Silverdale (Washington) | 1,012.99 mi (1,630.26 km) |
| Boulder to Silverton (Oregon) | 954.27 mi (1,535.75 km) |
| Boulder to Simi Valley (California) | 841.80 mi (1,354.74 km) |
| Boulder to Simpsonville (South Carolina) | 1,310.32 mi (2,108.76 km) |
| Boulder to Sioux City (Iowa) | 490.64 mi (789.62 km) |
| Boulder to Sioux Falls (South Dakota) | 501.36 mi (806.86 km) |
| Boulder to Skokie (Illinois) | 921.61 mi (1,483.19 km) |
| Boulder to Sleepy Hollow (New York) | 1,639.97 mi (2,639.28 km) |
| Boulder to Slidell (Louisiana) | 1,100.02 mi (1,770.31 km) |
| Boulder to Smithfield (North Carolina) | 1,496.00 mi (2,407.58 km) |
| Boulder to Smithfield (Utah) | 365.13 mi (587.62 km) |
| Boulder to Smithville (Missouri) | 568.90 mi (915.56 km) |
