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Library of Congress Geography & Maps: An Illustrated Guide

Digital Data and Geographic Information Systems

On a planet of finite resources faced with mounting population pressures, geographic information systems already have become indispensable for resource management, policy assessments, and strategic decisions.

Chairman, House Science, Space, and Technology Committee (now the House Committee on Science), quoted in GISDEX Express, 1992

Since its early beginnings in the 1960s, GIS has revolutionized the nature of cartography. Geographic Information Systems (GIS) allows geospatial data, encompassing areas ranging from regions to world boundaries and subjects from nautical to energy data, to be digitally represented in varied ways.

GIS treats data as different layers. For example, one layer may contain the street pattern of a city, another the administrative districts of the city, and a third might show the location of reported crimes. Within GIS, the portrayal of each type of data can be tailored to meet specific criteria, and then the various layers combined to form a single map. One of the key features of a GIS is that any type of information with a geographic component can be mapped. Thus, thematic maps can be constructed from layers of data that represent traditional cartographic information and from datasets from other sources.

GIS map produced from statistical data about uterine cancer rates in South Dakota
National Cancer Institute (U.S.). Uterine cancer rates in South Dakota, by county, 1953-1987. [after 1987]. Library of Congress Geography and Map Division.

Because GIS can be used to build and customize maps for analysis, it can be used to communicate a variety of issues, including medical and environmental issues. For instance, a map created by the U.S. National Cancer Institute in the late 1980s, "Uterine cancer rates in South Dakota, by county, 1953-1987," shows disproportionate rates of uterine cancer mortality in Oglala Lakota County (called Shannon County at the time of this map’s creation), the entirety of which is part of the Pine Ridge Indian Reservation.

The Geography and Map Division contains, acquires, and uses GIS data to make maps for Congress, alongside the Congressional Research Service (CRS). Datasets from federal sources are commonly used in GIS maps. Federal data is available through the GeoPlatform Portal External, which was developed by the Federal Geographic Data Committee (FGDC). The GeoPlatform Portal External was recognized as an access for data point by the Geospatial Data Act of 2018 External. Additionally, the Library of Congress publishes guidance for GIS, geospatial, and non-GIS cartographic data in the Recommended Formats Statement.

The division also oversees the production of StoryMaps for the Library of Congress (CSV files providing the mapped data are available for download). These are immersive web applications that tell the incredible stories of the Library’s collections through narrative, multimedia, and interactive maps.

GIS Maps from the Digital Collections