The Federal Charter or Letter of Alliance () 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. The Charter documents the Eternal Alliance of the League of the Three Forest Cantons (), the union of three cantons in what is now central Switzerland. It is dated to early August 1291, which in the 20th century inspired the date of Swiss National Day, 1 August. Done in Latin, the Charter makes reference to a previous (lost or unwritten) pact. It is now exhibited at the Museum of the Swiss Charters of Confederation in Schwyz. Contents The Alliance was concluded between the people of the alpine areas of Uri, Schwyz and Unterwalden (). The participants are referred to as conspirati and (synonymously) coniurati, traditionally translated in German as "Eidgenossen" (and in English as "Confederates"). The Charter was probably intended to ensure legal certainty after the death of Rudolf I of Habsburg on 15 July 1291. The first two paragraphs commit all three communities to the joint defence of the three valleys. The remainder of the Charter concerns judicial matters: It calls for arbitration in the case of conflicts, rejects foreign judges, establishes the death penalty for murderers and exile for arsonists, and commands obedience to judges and judicial verdicts. Date and context The authenticity of the letter used to be disputed as a supposed modern forgery. But historians now agree that it is certainly a product of the 14th century. In 1991, the parchment was radiocarbon dated to between 1252 and 1312 (with a certainty of 85%). The document is thus not a forgery tied to the emergence of the modern federal state in 1848. It should rather be seen in the context of chapter 15 of the Golden Bull of 1356, where Charles IV outlawed any conjurationes, confederationes, and conspirationes, meaning in particular the city alliances (Städtebünde), but also other communal leagues that had sprung up through the communal movement in medieval Europe. It was then very common to produce documents only when needed. At the time, agreements were most often verbal, and any