A case map is one which was dissected into parts, then backed with linen or cloth–with a slight separation between the sections–so that it could then be folded up into a smaller, portable form. The maps often had a slip case to keep them protected. The maps are similar in intent to what are called “pocket maps,” which were printed on thin paper to be folded up, though case maps tend to be of a larger size.
These maps appeared first in the eighteenth century, and these are often called ‘saddle bag’ maps, as they could easily fit into a saddle bag. They continued to be issued into the late nineteenth and twentieth century. Some of the maps were simply travelers maps, showing information needed for travelers and small enough to carry, while others were issued related to current political or military events. For these reasons, case maps are generally very current and contain detailed information that is time specific.
Being issued separately, these maps were subject to the vicissitudes of time, so many were lost or destroyed over time. Thus case maps are not only some of the most historically interesting maps, but they are also among the rarest maps.