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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.

How to View Map Information

Because mapping and database information is being added to the Maryland Inventory of Historic Properties, National Register, and other databases as properties are documented, the best source of up-to-date GIS information is found by visiting the MHT Library. Mapping information is available on workstations there, and qualified visitors can also view property boundaries on physical USGS topo maps. For more information and to schedule a library visit, see below.

Some GIS data has been exported to online applications and "web services" on the State of Maryland web sites. Please note that these should not be used exclusively by consultants working on research or compliance-based studies, as the data may be seriously out of date. Check the metadata Note also that archeological information will not be found on these sites, because of the sensitivity of site location data.

Finally, it is possible to obtain GIS data electronically for users with a legitimate need and who cannot obtain this information in a Library visit. See Obtaining Data Products (below) for details.

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 the librarian, Mary Louise de Sarran, by email at, by phone at (410) 697-9546, or write to:

Maryland Historical Trust Library
ATTN: Mary Louise de Sarran
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 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.

NOTE: As of April 2016, MD iMap data is being updated to incorporate all newly-registered architectural and archeological properties. This is being done in conjunction with the development of "map-based" Medusa, the MHT's central cultural resource information system. As these are being developed, it is possible that new resources (those accessioned within the past five years) will not be reflected in the iMap data; for that reason, we recommend using iMap only for general queries, but to visit the MHT Library (see above) if you need comprehensive information.

Once the services and map-based Medusa have been fully updated, instructions for their use will be posted here.

Other Online GIS Websites

MHT information is sometimes found on other external websites, such as the Maryland Department of Natural Resources’ GIS website: MERLIN Online. We suggest that you carefully check the metadata to make sure that it has been updated fairly recently, and to visit the MHT Library if you need comprehensive information.

GIS Data for Users with Desktop GIS Software

The GIS data are also available as a web service through MD iMAP. The same cautions given in the last few paragraphs apply here as well.

Map Service Links

National Register of Historic Places:

Maryland Inventory of Historic Properties:

Maryland Historic Trust Preservation Easements: