SCHLESWIG-HOLSTEIN. — Former duchy, ceded by Emperor Conrad II to Denmark in 1035 and governed, with the title of dukes, by members of the Danish royal house; inherited in 1386 by the Counts of Holstein-Schauenburg; returned to Denmark in 1459 after their extinction; made a province of Prussia in 1867.
The first missionaries were St. Willibrord and Atrebane, who died a martyr in 780 during the rebellion of the Saxons. Under Louis the Pious, Ebbò, archbishop of Reims, and St. Ansgar, companion of King Harald of Denmark, who had been converted to Christianity in 826, attempted the mission once more. As a result of the incursions of the Normans and the Wends, everything was again destroyed.
Under Henry I, the March on the Eider was reconstituted, thus inaugurating a new missionary era. In 948 the archbishop of Bremen, Adaldag, founded the diocese of S. and those of Ribe and Aarhus in Denmark. Under the son of Harald, the Viking Sven Forkbeard, who returned in 985, the diocese of Aarhus was suppressed and the bishops of Ribe and S. were expelled. In the final years of his life Sven Forkbeard became a Christian. His son Canute the Great propagated Christianity throughout his entire kingdom (Denmark, England, Norway). When Canute also became margrave of S., S.-H., until then part of the ecclesiastical province of Bremen-Hamburg, passed to the Danish province of Lund, erected in 1104, with which it remained united until its suppression by Christian III of Denmark. The last Catholic bishop of S., Godescalco von Ahlefeld (1527–41), was unable to overcome the policy of the kings of Denmark, who were inclined toward reform. Christian III proclaimed Lutheranism the state religion in 1536 and prohibited the practice of the Catholic religion. Upon Godescalco’s death, Tileman von Hussen became the first Lutheran bishop of S. In 1542 the ecclesiastical regulation of S.-H., identical to the Danish one of 1537, was proclaimed the fundamental law of the state. Only at the beginning of the seventeenth century did some Catholic communities manage to form. From 12 November 1669 the territory belonged to the newly re-established Apostolic Vicariate of the Northern Missions. On 29 July 1868 the Apostolic Prefecture of S.-H. was erected and placed under the bishop of Osnabrück as pro-vicar. After the Concordat with Prussia of 14 June 1929, the Apostolic Prefecture of S.-H., by the constitution Pastoralis Officii Nostri of 13 August 1930, was incorporated into the diocese of Osnabrück.