ZIP code 57421 is officially located in the state of South dakota, primarily serving the city of Amherst. It falls under the administrative jurisdiction of Marshall County. When planning mail delivery, logistics routing, or demographic research, 57421 operates within the Central Time (CT) timezone and supports the 441 area codes.
According to the latest US Census Bureau and American Community Survey (ACS) datasets, the total population residing within the 57421 ZIP Code Tabulation Area is approximately 38,241. Understanding local economics is critical for market analysis; the median household income in this postal area sits at $97,421.