An old fortification of the Frankopans, built during the wars against the Turks, "Slovin" was first mentioned in the 12th century. The old fort was property of the Frankopan (Hungarian "Frangepán") family since the 15th century, joined by an old Franciscan monastery from the same period. Later, this town has been called Slunj. In the 16th century the town was ravaged by the Ottoman wars and turned into a military outpost of the Croatian Military Frontier, but by the end of the 17th century the settlement was rebuilt into the Slunj as it exists today. The castle has been developed to a fortress and served as headquarters for the commanding general of this area (see Stari grad Slunj). After the Treaty of Sistova in 1791 people increasingly began to re-settle in this area.