The 1300-km-long, up to 300-km-wide onshore segment of the East Greenland Caledonian orogen is divided into distinct structurally bound geological domains that originally evolved as major westward-displaced thrust units during collision with Baltica. The thrust systems accommodated contraction of an already complex Laurentian assembly of Archean to Neoproterozoic and Cambrian to Silurian lithostrati graphic units and are a consequence of the convergence, and final collision, of Baltica with Laurentia in the mid- to late Silurian Scandian orogeny. The transition from undisturbed foreland to orogen is perfectly preserved in the extreme north of the East Greenland Caledonides, where a younger lower (Vandredalen) thrust sheet carrying older thrust sheets (Western thrust belt) is displaced westward across a thinskinned fold-and-thrust belt. In the southern half of the orogen, a pile of far-traveled thrust sheets (from youngesto oldest, Gemmedal, Niggli Spids, Hagar Bjerg thrust sheets) is displaced WNW across parautochthonous foreland windows, and the intact foreland is only intermittently exposed at the margin of the Inland Ice in the far west. These westward- and foreland-propagating systems are distinct from the Nørreland thrust sheet, the coastal region between 76°N and 79°N, in which Paleoproterozoic basement gneiss litholog t ies host enclaves of Devonian and Carboniferous eclogitefacies rocks. These rocks must have been exhumed from the roots of the collisional orogen, and their age suggests that the Nørreland thrust may be out of sequence relative to the main WNW foreland-propagating systems.