New Holstein is a city in Calumet County in the U.S. state of Wisconsin. The population was 2,891 as of 2024. The city is located within the Town of New Holstein. New Holstein is named after the German duchy of Holstein from which many early settlers emigrated. In 1848, 70 people from Hamburg, Germany emigrated to the New Holstein area, forming the basis of what would become the present city. Many settlers were intellectuals who feared an impending war as a result of competing claims to the territory. Settlers originally named the community Altona after Altona, Hamburg, Germany. As the amount of mail received in Altona increased, the United States Post Office wanted Altona to be renamed because the community's name was too close to Altoona in western Wisconsin.