Research on medieval Iceland--focusing on the period of the Commonwealth, from the establishment of the National parliament of 36 chiefdoms in 930 to submission to the Norwegian King in 1264--generally assumes a perennial subsistence economy, neglects the significance of trade, and lacks focus on changes in farming systems and tributary relations. This dissertation deals with the formation of chiefdoms, communities, ecclesiastical institutions and state, and with production for market, subsistence and tribute in early Iceland in the context of climatic change and ecological succession. Based on the integrative use of narrative, legal and economic documents, and archaeological and ethnographically derived data, it is argued that foreign markets and domestic credit exchanges were key to productive relations and land tenure and farming systems prior to 1200. This dissertation describes (1) chiefdom formation in terms of the economic rule of merchant-farmers, (2) the integration of a broad-based subsistence economy supporting specialized sheep production and yielding surplus wool for export, (3) freeholder production intensification in the context of mercantile activity, (4) disintensification and a change to a farming system emphasizing sheep reared for efficient milk and meat production, (5) the rise of rent tenure, communal property rights, and tributary systems in contexts of developing ecclesiastic institutions and colonial relations with Norway. The sagas are examined to show how trade enterprises were facilitated through class, transmission of property, a cognatic ego-centered kinship system, marriage, fostering, and household networks. An extensive analysis of Bjarnar saga Hitdaelakappa reveals changes in the modes and means of production and shows the saga employing symbolism relating to marriage and kinship that reflects successive formation of different institutions and professional careers, as well as historically transforming links between Iceland and Norway, secular and ecclesiastical authority, and wealth accumulation and succession. A new model is proposed for looking at the 'secondary exploitation' of livestock and for characterizing levels and means of intensification and specialization in Northern farming. This model is applied to evidence from England pertaining to the period from Iron Age to the 15th century.