This article traces the diachronic development from the Proto Norse demonstrative hinn via the Old Icelandic definite article(s) to the Modern Icelandic article system. This demonstrative gave rise to two distinct article elements during the Viking period that are well-attested from Old Icelandic onwards, a freestanding and a suffixed article.
Based on evidence from Old Icelandic, I argue for a categorial distinction between an adjectival and a nominal article, which does not entirely coincide with a mere morpho-phonological distinction. The former, which mostly occurs as a freestanding element, is a genuine component of AP, not an immediate constituent of the nominal extended projection. The latter, which only occurs in suffixal form, heads a low projection in the extended nominal projection and has scope only over the noun. For Modern Icelandic, on the other hand, I will adopt the idea that free and suffixed articles are two surface manifestations of the same element.
The diachronic perspective is complemented by an examination of the development of seven adjectivally modified definite noun phrase patterns. This empirical survey reveals several surprising facts: The standard pattern of modification in Modern Icelandic was virtually non-existent prior to the 17th century, and double definiteness persisted until the early 20th century. Likewise, certain modificational patterns otherwise found in Mainland Scandinavian were dominant between the 16th and 19th century. This latter observation points to a competition between two adjectival articles hinn vs. sá similar to the one that had taken place earlier in Mainland Scandinavian. In Icelandic, however, sá did not replace hinn, and, in the long run, a pattern not comprising an adjectival article became the dominant one.