Originally inhabited by Celts, the territory was conquered by the Romans and became part of the province of Noricum. After the fall of the Roman Empire, its history followed that of the city of Salzburg. An ancient Celtic settlement, and later a Roman trading center named Juvavum, the town developed in the early 8th cent. around the late 7th-century monastery of St. Peter.
By c.798 Salzburg was the seat of an archbishopric, and for almost 1,000 years it was the residence of the autocratic archbishops of Salzburg, the leading ecclesiastics of the German-speaking world. They became princes of the Holy Roman Empire in 1278 and wielded their power with extreme intolerance. In the late 15th cent. the Jews were expelled, and in 1731–32 some 30,000 Protestants migrated to Prussia after a period of severe persecution. Secularized in 1802, Salzburg was transferred to Bavaria by the Peace of Schönbrunn (1809). The Congress of Vienna (1814–15) returned it to Austria.