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Geographic Information System (GIS) Data

The Maryland Historical Trust maintains a geographic information system (GIS) and related database on Maryland’s architectural, archeological, and cultural resources.

The system is designed to facilitate Trust staff responsibilities in the areas of research, review and compliance. Currently, the information is available to researchers at workstations in the library, and GIS data is distributed on disk to consultants, government agencies, and non-profit organizations for planning and research purposes. Eventually the data will be incorporated into Medusa, the State's online cultural resource information system.

The Maryland Historical Trust has been developing GIS data on historic properties since 1991. The primary system data consist of the National Register of Historic Places, state inventories of historic properties and archeological sites, the statewide record of archeological survey coverage, and MHT Historic Preservation Easement holdings. The Maryland Historical Trust also develops and maintains the Maryland Heritage Area boundary files.

Medusa, Maryland's Cultural Resource Information System

Through Medusa, you may access information about architectural and archeological resources recorded in the Maryland Inventory of Historic Properties (MIHP) and the National Register of Historic Places (NRHP), as well as properties on which MHT holds preservation easements. Medusa also includes information on resources that have been evaluated for National Register eligibility (Determinations of Eligibility - DOEs).

» Go to Medusa

User accounts are required for access to archeological site data; they are not required for access to architectural records.

Full User Accounts. If you meet the Secretary of the Interior's Professional Qualification Standards for Archeology, you can obtain a "full" account that allows you off-site (remote) as well as in-Library access to the archeological data. Please allow up to two weeks for processing your request.

Proxy Accounts. An archeologist with a valid Medusa account can also request one or more "proxy" accounts for individual co-workers or students who need access to the archeological database for compliance or research projects. Typically proxies are people who work for contract firms or who are students working under a professor's guidance, and who may not meet the Secretary's Standards on their own.

» Submit Account Request

For More Information About Requesting an Account. Please contact Gregory Brown at 410-697-9538 or

Visiting the MHT Library to Use GIS Data

The library is open to the public on Tuesdays, Wednesdays, and Thursdays by appointment only. All material relating to Maryland's archeological sites is accessible only to qualified researchers with prior approval from the Office of Archeology. For further information or to schedule an appointment, contact Lara Westwood by email at, by phone at (410) 697-9546, or write to:

Maryland Historical Trust Library
ATTN: Lara Westwood
100 Community Place
Crownsville, MD 21032

Obtaining Data Products

GIS data are available to outside users for research and planning purposes, provided in shapefile format on CDs. Fees cover the cost of producing the files and transferring them to CD. Use the order form/license agreement to order data.

Three historic sites GIS data sets are commonly distributed:

National Register of Historic Properties
This data layer depicts boundaries of historic properties in Maryland that are listed on the National Register of Historic Places, a listing maintained by the U.S. Department of the Interior.
Maryland Historical Trust Historic Preservation Easements
This data layer depicts properties where owners have entered into an easement agreement with the Maryland Historical Trust to protect the historic character of the property.
Maryland Inventory of Historic Properties
This data layer depicts all historic properties which have been listed on the state inventory.

Each set consists of a digital file of the property locations and a database table which contains identification and attribute information. See order form for pricing.

Maryland Archeological Site Survey

Because of the sensitivity of archeological site information, access to archeological site location data is restricted and is generally available only to those who meet the Secretary of the Interior's Professional Qualification Standards. Qualified individuals who wish to obtain this data layer should contact or by phone at 410-697-9539.

On-Line GIS Data

As part of Maryland's open data policy, MHT's GIS data (excluding archeological site locations) is also available through the Maryland Integrated Map (MD iMap), Maryland's mapping and GIS data portal. The data available online includes National Register of Historic Places, the Maryland Inventory of Historic Properties, MHT Preservation Easements, and Maryland Heritage Areas. Data online does not include Determination of Eligibility information or archeological site information.

Online metadata and version info is found in the Map Service information on MD iMap.

Map Service Links

National Register of Historic Places:

Maryland Inventory of Historic Properties:

Maryland Historic Trust Preservation Easements: