He appears to have attracted the notice of the Frankish king, through whose influence in 798 Salzburg was made the seat of an archbishopric; and Arno, as the first holder of this office, became metropolitan of Bavaria and received the pallium from Pope Leo III.
He established a library at Salzburg, furthered in other ways the interests of learning, and presided over several synods called to improve the condition of the church in Bavaria.
Aided by a deacon named Benedict, Arno drew up about 788 a catalogue of lands and proprietary rights belonging to the church in Bavaria, under the title of Indiculus or Congestum Arnonis.
[2] Many other works were produced under the protection of Arno, among them a Salzburg consuetudinary, an edition of which appears in Quellen and Erörterungen zur bayerischen und deutschen Geschichte, vol.
It has been suggested by Wilhelm von Giesebrecht that Arno was the author of an early section of the Laurissenses majores, surviving in the copy at Lorsch Abbey, which deals with the history of the Frankish kings from 741 to 829; and of which an edition appears in the Monumenta Germaniae Historica, Scriptores, Band i, pp.