The first mention of the Saxon noble Adalbert of Haimar, Count of Wernigerode, in an 1121 deed is also the first documentation of the settlement, which had been founded about a century earlier in connection with the deforestation of the area. The counts built the castle on a slope south of the town as their residence; it was first mentioned as a castrum in 1213. When the line became extinct in 1429, the Wernigerode lands were inherited by the neighbouring County of Stolberg. The castle became the seat of the subordinate Amt administration and was put in pledge several times.

 Wernigerode town and schloss, about 1820

When in 1645 the Stolberg-Stolberg line split, Wernigerode again became the capital of the County of Stolberg-Wernigerode. The counts however struggled with the citizens in the course of the Thirty Years' War and had to take their residence at nearby Ilsenburg House. The castle was also heavily damaged during this war. It was not until 1710 that Count Christian Ernest could relocate the seat of government back to Wernigerode, when he had the castle rebuilt as a schloss in a Baroque style. He ruled for 61 years, though he had to accept the overlordship of King Frederick William I of Prussia in 1714.

 The castle chapel St. Pantaleon und Anna

Christian Ernest's descendant Count Otto, first president of the Prussian Province of Hanover from 1867, president of the Prussian House of Lords from 1872 and German Vice-Chancellor from 1878, had the schloss again extensively rebuilt in a Neo-Romantic half timber and half stone,[1] style known as historicism, finishing the project in 1893. Later when Otto became German ambassador the castle became a representation of North-German historicism. The entire complex includes a chapel built in 1880 by German architect Carl Frühling according to drafts by the renowned Vienna architect Friedrich von Schmidt. The original chapel was inaugurated in honor of patron saint Panthaleon and St. Anna and it was situated on the north-western part of the castle circle. Its baroque shape remained unchanged until its demolition in 1870. The new chapel is located in the same location as the old chapel and was inaugurated in 1883. The historic hall is decorated with built-in galleries, while the choir is decorated with stained glass designed by artist Carl Christian Andrea. The interior is full of French limestone and the niches placed throughout were sculpted by sculptor Karl Dopmeyer. The chapel is in its original state and can be used for concerts and weddings.[2] In 1945 the building was seized by the Soviet Military Administration in Germany. Now, it is open to the public and one of the most frequently visited in Saxony-Anhalt.[1]