THE Valtelline is, strictly speaking, that portion of the upper valley of the Adda, about sixty miles in length, which lies between Sondalo, at the southern end of the Serra di Bormio and an imaginary line drawn between the villages of Piantedo and Dubino, a few miles from the point where the Adda falls into the Lake of Como. The Valtelline proper is divided into four districts, the terzero di Sopra, with Tirano for its capital; the terzero di Sotto, with Sondrio for its capital; the so-called Squadre, with Morbegno as its capital; and the independent district of Teglio. But intimately associated with the Valtelline, sharing its vicissitudes, and for historical purposes to be considered a part of it, we have the county of Bormio, commanding the Wörmserjoch and the uppermost reaches of the Adda, and the county of Chiavenna, the key to those two important passes the Splügen and the Maloggia. The Valtelline proper runs nearly due east and west; above Tirano it takes a more northern trend towards Bormio. Debouching as it does on the head of Como, it forms one of the "gates of Italy," and is a connecting link of great value between the Lombard plain and Tyrol, leading over the Wörmserjoch by Santa Maria and the Vintschgau to Meran. At the period with which we are dealing, a private report to Venice placed the population at 80,000, and Padavino, secretary to the Council of Ten and the ablest Venetian envoy to the Grisons, gives the fighting forces of the whole district thus: the Grey League, 10,200 men; the Gotteshaus, 10,600; the Zehngerichten, 5000; Valtelline and Bormio, 15,000; and Chiavenna, 2000; thus indicating that the Valtelline with the counties of Bormio and Chiavenna was the most populous part of the whole Graubünden. The people of the Valtelline were strictly, even bigotedly Catholic, while their masters, the Graubündners, were partly Protestant, partly Catholic, and in both cases of a very deep dye.
The Valtelline, with Bormio and Chiavenna, came into the possession of the Grisons in the following manner. When Gian Galeazzo Visconti, after murdering his uncle Bernabò, seized the whole of the Milanese duchy, Bernabò's son Giammastino fled to Chur; and in January, 1386, out of gratitude for the protection granted to him by Bishop Hartmann,