The area of Dej / Dés/ Desch is inhabited since prehistoric times. A fortress was built by king Endre II for the protection of the busy salt traffic route from Ocna Dej / Désakna, where even the Romans have mined salt. Dés was first mentioned in written in 1236. The fortress was demolished by the Mongols. Károly Róbert settled the Saxons, granted Dés the the status of royal free town. The town had to be rebuilt several times. In 1602 general Basta killed most of the citizens, in 1661 Dés was attacked and burned up by the Turks, in 1686 and 1689 robbed by the Germans, in 1697 conflagration destroyed the town. During the war for independence led by Rákóczi Ferenc II, the Germans set Dés on fire in 1703 and 1706. In 1717 the Mongols ruined it, the same year when the salt mines were closed. In 1849, at the end of the war for independence the Russian army demanded 30 000 silver forints as a contribution for their expences. In 1514 the town took part in the uprising on the side of Dózsa. In 1638 the trial against the Sabaatians took place here resulting death sentences for many. Pápai Páriz Ferenc (professor of philosophy and medicines) was born here in 1614.

The Reformed Church was built int 14th century, rebuilt in the 15th and 18th centuries. The churchtower is 72 ms high, the choir was painted by Umling Lőrinc, the pulpit as made by Sípos Dávid in 1752.