Graubünden or Grisons (; ; ; see also other names) is the largest and easternmost canton of Switzerland. The canton shares borders with the cantons of Ticino, Uri, Glarus and St. Gallen and international borders with Italy, Austria and Liechtenstein. The name Graubünden translates as the "Grey Leagues," referring to the canton's origin in three local alliances, the League of God's House, the Grey League, and the League of Ten Jurisdictions. Graubünden is also home to three of Switzerland's ethnic groups and the subsequent languages of Swiss German, Italian and Romansh are all native to the state. It is also the only canton where the Romansh language is still spoken.
Most of the lands of the canton were once part of a Roman province called Raetia which was established in 15 BC. The current capital of Graubünden, Chur, was known as Curia in Roman times. The area later was part of the lands of the diocese at Chur.
In 1367 the League of God's House (Cadi, Gottes Haus, Ca' di Dio) was founded to resist the rising power of the Bishop of Chur. This was followed by the establishment of the Grey League (Grauer Bund), sometimes called Oberbund, in 1395 in the Upper Rhine valley. The name Grey League is derived from the homespun grey clothes worn by the people and was used exclusively after 16 March 1424. The name of this league later gave its name to the canton of Graubünden. A third league was established in 1436 by the people of ten bailiwicks in the former Toggenburg countship, as the dynasty of Toggenburg had become extinct. The league was called League of the Ten Jurisdictions (Zehngerichtebund).
The first step towards the canton of Graubünden was when the league of the Ten Jurisdictions allied with the League of God's House in 1450. In 1471 the two leagues allied with the Grey League. In 1497 and 1498 the Leagues allied with the Old Swiss Confederacy after the Habsburgs acquired the possessions of the extinct Toggenburg dynasty in 1496, siding with the Confederacy in the Swabian War three years later. The Habsburgs were defeated at Calven Gorge and Dornach, helping the Swiss Confederation and the allied leagues of the canton of Grisons to be recognised. However the Three Leagues remained a loose association until the Bundesbrief of 23 September 1524.
The last traces of the Bishop of Chur's jurisdiction were abolished in 1526. The Musso war of 1520 drove the Three Leagues closer to the Swiss Confederacy.
In response, in February 1621, Jenatsch led a force of anti-Habsburg troops to attack Rietberg Castle, the home of a leader of the pro-Catholic faction, Pompeius Planta. They surprised Planta and according to legend he was killed by Jörg Jenatsch with an axe. The murder of Planta encouraged the Protestant faction and they assembled a poorly led and disorganized army to retake the Valtellina and other subject lands. However, the army fell apart before they could attack a single catholic town. This Protestant invasion provided the Spanish and Austrians an excuse to invade the Leagues. By the end of October, Spain and Austria had occupied all of Graubünden. The resulting peace treaty of January 1622, forced Graubünden to cede the Müstair, the Lower Engadine and Prättigau valleys. The treaty also forbade the Protestant religion in these valleys. In response, in 1622, the Prättigau valley rebelled against the Austrians and drove them out of the valley. The Austrians invaded the valley twice more, attempting to reimpose the Catholic faith, in 1623–24 and 1629–31.
In 1623 the Leagues entered into an alliance with France, Savoy and Venice. Jürg Jenatsch and Ulysses von Salis used French money to hire an 8,000-man mercenary army and drive out the Austrians. The peace treaty of Monzon (5 March 1626) between France and Spain, confirmed the political and religious independence of the Valtellina. In 1627 the French withdrew from the Valtellina valley, which was then occupied by Papal troops. Starting in 1631 the League, under the French Duke Henri de Rohan, started to expel the Spaniards. However, Richelieu still did not want to hand the valley over to its residents. When it became clear that the French intended to remain permanently in the Leagues, but would not force the Valtellina to convert to Protestantism, Jürg Jenatsch (now a mercenary leader) converted in 1635 to the Catholic faith. In 1637, he rebelled and allied with Austria and Spain. His rebellion along with the rebellion of 31 other League officers forced the French to withdraw without a fight. On 24 January 1639, Jürg Jenatsch was killed during Carnival by an unknown attacker who was dressed as a bear. The attacker may have been a son of Pompeius Planta or an assassin hired by the local aristocracy. According to legend he was killed by the same axe that he used on Pompeius Planta. On 3 September 1639 the Leagues agreed with Spain to bring the Valtellina back under League sovereignty, but with the promise to respect the free exercise of the Catholic faith. Treaties with Austria in 1649 and 1652, brought the Müstair and Lower Engadine valleys back under the authority of the Three Leagues.
In 1798, the lands of the canton of Graubünden became part of the Helvetic Republic as the Canton of Raetia. With the Act of Mediation the "perpetual ally" of Switzerland became a canton in 1803. The constitution of the canton dates from 1892. In the following century, there have been about 30 changes made to the constitution.
The arms of the three original leagues are were combined into the modern cantonal coat of arms in 1933.