In the mid-nineteenth century the Jesuits gained a considerable influence here and congregated in large numbers.
The city was the ancient Sedanum, and in olden time the bishop bore also the title of "Prince of the Holy Empire." The power of this prelate was practically unlimited, and ordinances of state were, as late as the beginning of the nineteenth century, made in his name, and his arms formed the embellishments of the public buildings and boundary posts.
Rudolf III., king of Burgundy, from the year 1000, made them counts of Valais.
St. Théodule was the first bishop of Sion,—in the fourth century,—and is the patron of the diocese.
In 1070 the bishop of Sion came to England as papal legate to consecrate Walkelin to the see of Winchester.
In 1516 Bishop Schinner came to England to procure financial aid from Henry VIII. to carry on war against France.
The cathedral in the lower town is a fifteenth-century work which ought—had the manner of church-building here in this isolated region kept pace with the outside world—to be Renaissance in style. In reality, it suggests nothing but the earliest of Gothic, and, in parts, even Romanesque; therefore it is to be remarked, if not admired.
Near by is the modern episcopal residence.
The records tell of the extraordinary beauty and value of the trésor, which formerly belonged to the cathedral: an ivory pyx, a reliquary, and a magnificent manuscript of the Gospels—given by Charles the Great to St. Maurice, and acquired by the town in the fourteenth century. This must at some former time have been dispersed, as no trace of it is known to-day.
Sion was formerly a suffragan bishopric of Tarantaise, which in turn has become to-day a suffragan of Chambéry.