Drawing on examples from Achill Island, County Mayo and from the north Antrim uplands, notions of marginality, isolation, and cultural stagnation associated with upland landscapes are explored in light of contradictory material and documentary data, raising questions about the materiality of marginality and challenging static, nationalist presentations of rural Irish life in the post-medieval period. Discussion of the Irish evidence is contextualized with reference to the twentieth-century construction of marginality in southern Appalachia.