| South Sioux City to Smolyan | 5,570.44 mi (8,964.76 km) |
| South Sioux City to Sofia | 5,466.21 mi (8,797.01 km) |
| South Sioux City to Sopot | 5,515.50 mi (8,876.34 km) |
| South Sioux City to Sozopol | 5,622.59 mi (9,048.68 km) |
| South Sioux City to Sredets | 5,610.39 mi (9,029.05 km) |
| South Sioux City to Stamboliyski | 5,535.78 mi (8,908.98 km) |
| South Sioux City to Stara Zagora | 5,556.25 mi (8,941.92 km) |
| South Sioux City to Svilengrad | 5,609.77 mi (9,028.05 km) |
| South Sioux City to Svishtov | 5,483.52 mi (8,824.87 km) |
| South Sioux City to Targovishte | 5,542.30 mi (8,919.48 km) |
| South Sioux City to Teteven | 5,485.62 mi (8,828.26 km) |
| South Sioux City to Troyan | 5,502.05 mi (8,854.70 km) |
| South Sioux City to Tryavna | 5,528.26 mi (8,896.88 km) |
| South Sioux City to Tutrakan | 5,500.35 mi (8,851.96 km) |
| South Sioux City to Varna | 5,585.89 mi (8,989.62 km) |
