What makes a map a treasure? Cartographic Treasures of the Newberry Library is an extended meditation on this simple question that defines a simple answer. The maps in this catalogue were selected from the approximately 300,000 historic maps in Chicago's Newberry Library. They include many of the Library's oldest, rarest, and most exquisite maps--treasures in the conventional sense of the word. But there are also "common" maps that are treasures because they capture so well the spirit of their age, illuminating the geographical outlook of the people who made and used them.