The two valleys of Svarfaðardalur and Hörgárdalur lie in the region of Eyjafjörður, North Iceland. Here the medieval history of these two valleys, from the settlement in 880 or so to 1500 is discussed. The primary focus is on the social and environmental history of the valleys, as it can be interpreted on the basis of archaeology, written sources and palaeoecology. Pre-Christian burials, early family churches, other evidence of settlement and of the cultural landscape is scrutinized and discussed. The result is a fresh and original look at a key period in Icelandic medieval history.