The Massachusetts Coastal Zone data layer was compiled by the Massachusetts Office of Coastal Zone Management (CZM) to represent the Massachusetts coastal zone as defined in the October 2011 Massachusetts Office of Coastal Zone Management Policy Guide ("Policy Guide"). Appendix 2 of the Policy Guide contains the most recent description of the official Massachusetts coastal zone and should be used in connection with the following two sources depicting maps of the boundary: (1) the CZM Coastal Atlas (Volume II of the 1977 Massachusetts Coastal Zone Management Program and Draft Environmental Impact Statement) and (2) this data layer developed by CZM to depict the coastal zone in digital map format, available at: http://www.mass.gov/czm/mapping/czboundary.htm. This boundary was created per the Federal Coastal Zone Management Act (CZMA) of 1972 (Public Law 92-583, 16 U.S.C. 1451-1456). The boundary description is the specification of the major roads, rail lines, other visible rights-of-way, or coordinates marking the inland boundary of the coastal zone. The actual boundary is 100 feet inland of the landward side of the described line, with the exception of municipal boundaries, where the municipal boundary is the limit of the boundary description. This dataset represents the actual boundary.

As described in Appendix 2 of the October 2011 Policy Guide, the official Massachusetts coastal zone includes the lands and waters within an area defined by the seaward limit of the state's territorial sea, extending from the Massachusetts-New Hampshire border south to the Massachusetts-Rhode Island border, and landward to 100 feet inland of specified major roads, rail lines, other visible rights-of-way, or, in the absence of these, at specified coordinates. The coastal zone includes all of Cape Cod, Nantucket, Martha’s Vineyard, and the Elizabeth Islands. The coastal zone includes all islands, transitional and intertidal areas, coastal wetlands, and beaches within the Commonwealth. In isolated instances where the boundary line might exclude coastal resource area(s), these resources are included in the coastal zone although the written description follows the boundary line. Tidal rivers and adjacent uplands are included, at a minimum, to the extent of vegetation affected by measurably saline water. Anadromous fish runs are included, as well as their floodplains, to the freshwater breeding area, if such area is within a coastal town. Land owned or controlled by the federal government is excluded by law from the coastal zone.