ZIP code 51003 is officially located in the state of Iowa, primarily serving the city of Alton. It falls under the administrative jurisdiction of Sioux County. When planning mail delivery, logistics routing, or demographic research, 51003 operates within the Central Time (CT) timezone and supports the 401 area codes.
According to the latest US Census Bureau and American Community Survey (ACS) datasets, the total population residing within the 51003 ZIP Code Tabulation Area is approximately 17,201. Understanding local economics is critical for market analysis; the median household income in this postal area sits at $91,003.