Map Collections is organized according to seven major categories. A map or collection of maps which portrays a subject or multiple subjects is found under the category which includes the main subject. For example, maps of the national parks are found in Conservation and Environment; a map of the Lewis and Clark expedition is in Discovery and Exploration; maps used by the American Colonization Society during the settlement of Liberia are in Immigration and Settlement; and when they become available, Civil War maps will be in Military Battles and Campaigns and railroad maps will be in Transportation and Communication. In general, a map will be assigned to only one category, unless an item is part of more than one core collection.
The distinctions between these categories may not always be apparent. Many maps which have been placed within one category show additional subjects which are contained in a different category. Maps showing the location of mines and minerals would be available under the Conservation and Environment category but since the advent of the railroad made the movement of natural resources possible, many maps in Transportation and Communication also show the location of mineral deposits.
Maps that are included in more than one core collection will be found in the category for each core collection. For example, a map showing railroads in Georgia during the Civil War will be in both the Military Battles and Campaigns and Transportation and Communication categories since it is included in both the Railroad Maps and Civil War Maps collections.
Maps or collections of maps which do not fit into one of the five thematic categories are divided into the final two categories based on the geographic area covered. Maps or collections of maps showing a city, town, village, or area within a city are found in Cities and Towns. Maps or collections of maps showing areas larger than a city are in General Maps.
Because items in Map Collections are generally assigned to only one category, searching at this level provides the most complete results by accessing the indexes for all categories simultaneously.
Individual maps as well as entire collections or sub-categories, such as Railroad Maps and Civil War Maps, will continue to the added in the appropriate categories.