| Sioux City to Smolyan | 5,567.96 mi (8,960.76 km) |
| Sioux City to Sofia | 5,463.72 mi (8,793.01 km) |
| Sioux City to Sopot | 5,513.01 mi (8,872.32 km) |
| Sioux City to Sozopol | 5,620.08 mi (9,044.64 km) |
| Sioux City to Sredets | 5,607.89 mi (9,025.02 km) |
| Sioux City to Stamboliyski | 5,533.29 mi (8,904.97 km) |
| Sioux City to Stara Zagora | 5,553.75 mi (8,937.90 km) |
| Sioux City to Svilengrad | 5,607.27 mi (9,024.03 km) |
| Sioux City to Svishtov | 5,481.02 mi (8,820.84 km) |
| Sioux City to Targovishte | 5,539.80 mi (8,915.44 km) |
| Sioux City to Teteven | 5,483.13 mi (8,824.25 km) |
| Sioux City to Troyan | 5,499.56 mi (8,850.68 km) |
| Sioux City to Tryavna | 5,525.76 mi (8,892.86 km) |
| Sioux City to Tutrakan | 5,497.84 mi (8,847.92 km) |
| Sioux City to Varna | 5,583.37 mi (8,985.57 km) |
