In the 1648 Treaty of Westphalia, the archbishopric was promised to the House of Hohenzollern of the Margraviate of Brandenburg upon the death of its incumbent administrator, August, Duke of Saxe-Weissenfels.

The Halle region (Saalkreis), an exclave of the province, was surrounded by the Principality of Anhalt, the County of Mansfeld (acquired by Prussia in 1790), and the Electorate of Saxony.

King Frederick William I's 'allodification of the fiefs', or efforts to modernize feudal land ownership laws, was opposed by the duchy's Junker nobility, which feared losing their tax-exempt status.

[9] The estates of Pomerania voluntarily raised 5,000 troops for the Prussian Army during the Seven Years' War; their initiative was duplicated by the nobility of Magdeburg and neighboring provinces.

The ducal territory west of the Elbe River, including the cities of Magdeburg and Halle, were made part of the Kingdom of Westphalia, a client state of the First French Empire.