Horn (since 1970 part of Horn-Bad Meinberg) was founded by Bernhard III, Edler Herr zur Lippe, after 1230. It was first mentioned in 1248. Horn was located on the old road, that run from Cologne to Hamlin - and today is known as "Bundesstrasse 1" (B1).

Horn got strongly fortified with a surrounding wall and a moat. The castle, was part of this fortification, though it was later used as a kind of retirement home by several widows of the House of Lippe.

Armed conflicts over the city took place in particular during the Soest feud (1444–1449) and during the Thirty Years' War (1618–1648). In 1864, large parts of the city were destroyed in a fire, about 60 houses burnt down including the town hall.
The former district court ("Amtsgericht") is a large baroque building with massive gable facades and a double flight of stairs. The entrance is marked "1756".

The district court was here between 1879 and 1970, when it was moved to Detmold.