Waldeck (välˈdĕk) [key], former principality, central Germany, now an administrative district (c.420 sq mi/1,090 sq km) of Hesse. Arolsen was the capital. An agricultural region, hilly and forested, it is drained by the Eder and Diemel rivers. A county of the Holy Roman Empire from c.1200, Waldeck was united with the county of Pyrmont in the late 17th cent., and its rulers were later raised (1712) to princely rank. In 1867 the prince of Waldeck-Pyrmont renounced most of his sovereign prerogatives in favor of Prussia; the title, however, continued in the family. Waldeck-Pyrmont became a republic in 1918. By a plebiscite in 1922, Pyrmont passed to Prussia and was incorporated into Hanover prov.; by another plebiscite (1929) Waldeck proper became part of the Hesse-Nassau prov. of Prussia. After World War II it was made part of Hesse.