Around 612 Gallus, according to tradition an Irish monk and disciple and companion of Saint Columbanus, established a hermitage on the site that would become the monastery.

[4] Following Gallus' death, his disciples remained living together in his cell and followed the rule of St. Columban, which combined prayer, work of the hands, reading, and teaching.

[8] A gentleman and judge of Thurgau, Waltraf (possibly, Waltram or Gaudran), in order to use the alms and collections that were being given at St. Gall's tomb to found a more regular monastery, attracted a local Alemannic pastor Otmar.

[9] Otmar extended St. Gall's original hermit cell and adopted the Carolingian style for his building projects.

The abbey grew quickly; many Alemannic noblemen entered to become monks and arts, letters and sciences flourished.

At Charlemagne's request Pope Adrian I sent distinguished cantors from Rome, who instructed the monks in the use of the Gregorian chant.

It was not until Emperor Louis the Pious (ruled 814–840) confirmed in 813 the imperial immediacy (Reichsunmittelbarkeit) of the abbey, that this conflict ceased.

King Louis the German confirmed in 833 the immunity of the abbey and allowed the monks the free choice of their abbot.

[10] In 1207, abbot Ulrich von Saxwas raised to the rank of Prince (Reichsfürst, or simply Fürst) of the Holy Roman Empire by King Philip of Germany.

However, he encountered stiff resistance from the St. Gallen citizenry, other clerics, and the Appenzell nobility in the Rhine Valley who were concerned about their holdings.

The mayor of St. Gallen, Ulrich Varnbüler, established contact with farmers and Appenzell residents (led by the fanatical Hermann Schwendiner) who were seeking an opportunity to weaken the abbot.

Initially, he protested to the abbot and the representatives of the four sponsoring Confederate cantons (Zürich, Lucerne, Schwyz, and Glarus) against the construction of the new abbey in Rorschach.

He was confident that the four sponsoring cantons would not intervene with force, due to the prevailing tensions between the Confederation and the Swabian League.

The people of Appenzell and the local clerics submitted to this force without noteworthy resistance, while the city of St. Gallen braced for a fight to the finish.

The new structures, including the cathedral by architect Peter Thumb (1681–1766),[13] were designed in the late Baroque style and constructed between 1755 and 1768.

[2] Lately the Stiftsbibliothek has launched a project for the digitisation of the priceless manuscript collection, which currently (December 2009) contains 355[2] documents that are available on the Codices Electronici Sangallenses webpage.

The library interior is exquisitely realised in the Rococo style with carved polished wood, stucco and paint used to achieve its overall effect.

[14] One of the more interesting documents in the Stiftsbibliothek is a copy of Priscian's Institutiones grammaticae which contains the poem Is acher in gaíth in-nocht... written in Old Irish.

The library also preserves a unique 9th-century document, known as the Plan of St. Gall, the only surviving major architectural drawing from the roughly 700-year period between the fall of the Western Roman Empire and the 13th century.

The plan was an ideal of what a well-designed and well-supplied monastery should have, as envisioned by one of the synods held at Aachen for the reform of monasticism in the Frankish empire during the early years of emperor Louis the Pious (between 814 and 817).

A late 9th-century drawing of Paul lecturing an agitated crowd of Jews and gentiles, part of a copy of a Pauline epistles produced at and still held by the monastery, was included in a medieval-drawing show at the Metropolitan Museum of Art in New York the summer of 2009.

A reviewer noted that the artist had "a special talent for depicting hair, ... with the saint's beard ending in curling droplets of ink.

A table of abbots' names complete with their coats of arms was printed by Beat Jakob Anton Hiltensperger in 1778.