The House of Ascania is an Old Saxon reigning family historically documented since the 11th century. It is also known as the House of Anhalt, which refers to its longest-held possession. Their ancestral seats, Ballenstedt, Anhalt, Aschersleben, and Bernburg, are located in the present-day Anhalt region in Saxony-Anhalt. The ruins of Anhalt Castle are situated in the Harz Mountains northeast of Harzgerode. The name "Askanier" derives from the Latinization of their seat at Aschersleben. Since the late 17th century, only the Anhalt branch has survived. Albert the Bear became Duke of Saxony in 1138 and, with the control of the Margraviate of Brandenburg in 1150, the first Margrave in the formerly Slavic settlement area. In 1180, eastern parts of the Stem Duchy of Saxony passed to the Askanier Bernhard of Saxony. As Dukes of Saxe-Wittenberg, the family received hereditary electoral dignity in 1356. The family ruled Anhalt-Dessau, Anhalt-Bernburg, Anhalt-Köthen, Anhalt-Zerbst, Anhalt-Plötzkau, and Anhalt-Aschersleben. Alexius Friedrich Christian of Anhalt-Bernburg was the first of the Anhalt princes to gain the title of Duke in April 1806.