South Sioux City, NE has a population of 13,268 and is the 3,147th largest city in the United States. The population density is 2,144 per sq mi which is 8844% higher than the Nebraska average and 2266% higher than the national average. The median age in South Sioux City is 32 which is approximately 11% lower than the Nebraska average of 36. In South Sioux City, 63% of the population over 15 years of age are married, 49% speak English and 43% speak Spanish. 15% of South Sioux City residents were born in Nebraska, 55% were born out of state, 1% were born outside of the United States and 29% were foreign born.