The settlement at Sillian evolved in AD 769, at the time the Benedictine abbey Innichen was founded. The oldest documented reference to Sillian is "SILANO" around AD 1000. It refers to a contract concluded by Bishop Albuin of Brixen concerning a land tax. By AD 1313 Silian had achieved the status of "village". It is assumed that the name Silian is derived from the Villgraten Creek, which was referred to in AD 1140 by the name of Sill or Siligan.
In AD 1797 the court was relocated from the old Heinfels fortress to the settlement of Sillian. The pillory (a wooden frame erected on a post, with holes for securing the head and hands, formerly used to expose an offender to public derision) located on the town square is the only remaining pillory in Eastern Tyrol and recalls the days of the medieval judicial system. Today, 2100 people live in the three districts of Ambach, Sillian and Sillianberg. The market town covers an area of 36.36 square kilometres (14 square miles)