In the 17th and 18th century, whaling was an important trade on Föhr. A census in 1787 showed that Utersum and Hedehusum together had 294 inhabitants, 62 of whom were seafarers. As a part of Western Föhr, Utersum belonged to the Danish Enclaves and was thus directly linked to the Danish Kingdom while Eastern Föhr and Wyk adhered to the Duchy of Schleswig. Only when Denmark lost Schleswig to Prussia after the Second Schleswig War of 1864 did Utersum become part of Schleswig-Holstein due to the annexation of Schleswig-Holstein by Prussia in 1867.