David Rumsey's collection of historical maps is one of the largest and most complete of its kind. Focused for the most part on North and South America in the eighteenth and nineteenth centuries, the collection is comprised of more than 150,000 items: maps, atlases, and contextual supporting documents. Unlike similar collections, the delicacy and rarity of which necessitate careful storage and restricted-use policies, The Rumsey Collection is available in growing numbers on the Web - and it is this conjunction of old and new technologies that is the heart of Cartographica Extraordinaire.