A Landtag was first called together in 1387, and the landgraves were con stantly at variance with the electors of Mainz, who had large temporal possessions in the country.
The most noteworthy of the landgraves were perhaps Louis I.
In 1345 it became a fief of the landgraves of Thuringia, to whom it escheated in 1385 with the extinction of the line of Otto III.
The town passed from the landgraves of Thuringia to the landgraves of Hesse in the 13th century, becoming one of the principal residences of the latter house in the 15th century.
It became a town in the 12th century and in 1370 the burghers, having meanwhile shaken off the authority of the abbots, placed themselves under the protection of the landgraves of Hesse.
It was richly endowed by Charlemagne and became an ecclesiastical principality in the 12th century, passing under the protection of the landgraves of Hesse in 1423.
Thus there were archbishops, bishops, abbots, dukes, Inargraves, landgraves, countsforming together a large body each of whom claimed to have no superior save the emperor, whose authority they and their predecessors had slowly destroyed.
Hildburghausen (in records Hilpershusia and Villa Hilperti) belonged in the 13th century to the counts of Henneberg, from whom it passed to the landgraves of Thuringia and then to the dukes of Saxony.
In spite of many vicissitudes (from 1109 to 1137, for instance, the town was subject to the landgraves of Thuringia), and of a charter granted in 1242 by the emperor Frederick II., the archbishops succeeded in upholding their claims. In 1255, however, Archbishop Gerhard I.
Hanoverian Minden), to distinguish it from Prussian Minden, was founded by the landgraves of Thuringia, and passed in 1247 to the house of Brunswick.
It was known as a town as early as 1200, about which time it came into the possession of the landgraves of Thuringia.
Above the town to the south, is the historic Wartburg, the ancient castle of the landgraves of Thuringia, famous as the scene of the contest of Minnesingers immortalized in Wagner's Tannhauser, and as the place where Luther, on his return from the diet of Worms in 1521, was kept in hiding and made his translation of the Bible.
Of Brabant, to defend the town against Henry III., margrave of Meissen, during the succession contest that followed the extinction of the male line of the Thuringian landgraves in 1247.
This Schloss was formerly the residence of the landgraves of Hesse, served afterwards as a prison, and is now the repository of the historically interesting and valuable archives of Hesse.
The church also contains the tombs of numerous Hessian landgraves and knights of the Teutonic Order.
On a neighbouring hill stands the palace of the former landgraves, built in 1680 and subsequently enlarged and improved.