The language of a speech community can only act as an identity marker for all of its speakers if linguistic norms are widely shared and if a minimal number of language varieties are spoken. This article examines briefly how a linguistic norm came to serve the whole of Iceland and how a situation of relative linguistic homogeneity was maintained for centuries. Sociolinguistic theory tells us that the speech community that we can reconstruct for early Iceland should lead to the establishment and maintenance of local norms. However, Iceland, arguably monodialectal, was certainly characterized by long-term linguistic homogeneity and remained a society where nucleated settlements barely formed over a thousand-year period. Scholars have argued that a mixture of dialects leveled shortly after the settlement of Iceland in the ninth century (Settlement). Studies show that dialect leveling requires dialect mixing, the convergence of people on one place, and sustained linguistic contact between the speakers. The settlement pattern of Iceland is indicative of population divergence (not convergence) and there is limited evidence of sustained contact. It is therefore proposed that the dialect leveling might be linked instead with significant population movements and social upheaval in mainland Scandinavia in the immediate pre-Viking period. The variety of Norse that was taken westward across the Atlantic might itself already have been the result of several earlier stages of mixing and koineization. It is only by combining linguistic, historical, and archaeological knowledge that this problem of how one linguistic norm came to serve the whole of Iceland can be understood.