Croatian Military Frontier
Until 1918, Slunj (named "SZLUIN") was part of the Austrian monarchy (Kingdom of Croatia-Slavonia, Modruš-Rijeka County, after the compromise of 1867), in the Croatian Military Frontier. It was administered by the "SZLUINER Grenz-Infanterie-Regiment N°IV" before 1881. Slunj became a district capital in the Modruš-Rijeka County in the Kingdom.