The Sioux City metropolitan statistical area, as defined by the United States Census Bureau, is an area consisting of four counties in three states – Iowa, Nebraska, and South Dakota, anchored by the city of Sioux City, Iowa. As of the 2020 census, the MSA had a population of 145,940. Plymouth County, Iowa, was removed from the definition of the MSA prior to the 2020 census.

Dixon County is a county in the U.S. state of Nebraska. As of the 2020 United States Census, the population was 5,606. Its county seat is Ponca. The county was created in 1856 and attached to Dakota County. It was organized in 1858.