There are 4 zip codes in Union County, South Dakota. The most populated is 57049, located in North Sioux City. * 2024 populations estimated based on the latest ACS 5-year data.

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Zip Code
Population
City
570497,661North Sioux City
570253,063Elk Point
570011,608Alcester
570381,577Jefferson

Zip Codes in Union County, South Dakota by Population (2024)