[1] According to the Peace of Westphalia of 1648, the former prince-bishopric was secularized as the Principality of Halberstadt and together with Magdeburg, Minden and Cammin given to the Brandenburg Elector Frederick William I of Hohenzollern as a compensation for Western Pomerania, which in the aftermath of the Brandenburg-Pomeranian conflict he had to cede to Sweden.

[2] This agreement was negotiated by Frederick William's representative Joachim Friedrich von Blumenthal, who in reward was appointed Halberstadt's first secular governor.

Lost territories included Weferlingen, which King Frederick I in 1703 ceded to his cousin Christian Heinrich of Brandenburg-Bayreuth-Kulmbach, a subdivision of the County of Hohenstein about the same time and Stapelburg left to Stolberg-Wernigerode in 1727.

[citation needed] The Principality of Halberstadt was dissolved according to the 1807 Treaty of Tilsit following Prussia's defeat in the War of the Fourth Coalition.

After the French final defeat at Waterloo, the principality was restored to Prussia in 1813 and incorporated into the new Province of Saxony in 1817.