The Federal Charter or Letter of Alliance (German: Bundesbrief) is one of the earliest constitutional documents of Switzerland. A treaty of alliance from 1291 between the cantons of Uri, Schwyz and Unterwalden, the Charter is one of a series of alliances from which the Old Swiss Confederacy emerged. In the 19th and 20th century, after the establishment of the Swiss federal state, the Charter became the central founding document of Switzerland in the popular imagination.