The MERLIN System has been in use at the Maryland Department of Natural Resources since 1994. It originally operated internally across the DNR network using the TNTatlas® software interface. The Maryland Department of Natural Resources (DNR) worked with MicroImages, Inc. during 1999 to create an Internet interface to DNR's MERLIN System. At that time, the existing MERLIN System provided access to over 150 gigabytes of geographic information products (spatial data) created by DNR and many other state, federal and private sources. These other sources include the Department of Planning, Department of Housing and Community Development, State Highway Administration, Virginia Institute of Marine Science, U.S. Fish & Wildlife Service, U.S. Geological Survey, the Federal Emergency Management Agency, SPOT Image Corporation and VARGIS, LLC. Since that time, the system has grown to include many more data layers from those and additional partners. In 2010, MERLIN Online was redesigned to take advantage of new online mapping technology.

MERLIN Online allows a user to produce a custom "map" for any location in Maryland, including their choice of base map and theme data layers. The identify tool allows users to point to a location on the map and received information about the data layers. Other features include the ability to measure distance and area, a map legend, hyperlinks from data layers to other web pages.

MERLIN Online should be used for guidance purposes only. The information contained in the spatial data provided in MERLIN is from publicly available sources. No representation is made as to the accuracy or completeness of the spatial data.