The region stretching across the Arctic from the Bering Straits to Greenland is one of the most critical for understating modern global climate change, especially as it affects keystone species and indigenous peoples. However, substantial changes in the arctic environment are not solely modern phenomena. The period between AD 900 and 1400 witnessed some of the most dynamic and variable arctic climates since the last Ice Age. Throughout the period from the Medieval Climatic Anomaly (an unusually warm period) to the Little Ice Age, this region also saw two of the greatest migrations in human history, an unprecedented level of warfare among hunters, the rise and fall of widespread cultures, hemispheric trade networks, and the beginnings of today’s indigenous northern peoples. The Northern World presents the Arctic as a dynamic, interactive, and connected region of peoples and landscapes that has proven remarkably adaptable to changing climate and social systems.