The U.S. Geological Survey (USGS) assisted the Massachusetts Department of Environmental Protection (MassDEP) with the Massachusetts Estuary Project (MEP), by delineating groundwater-contributing areas to various hydrologic features including ponds, streams, and coastal water bodies, throughout southeastern Massachusetts. These contributing areas were delineated over a 6-year period from 2003 to 2008 using previously published USGS groundwater-flow models for the Plymouth-Carver region (Masterson and others, 2009), the Sagamore (western) and Monomoy (eastern) flow lenses of Cape Cod (Walter and Whealan, 2005), and lower Cape Cod (Masterson, 2004). The original USGS groundwater-contributing areas were subsequently revised in some locations by the MEP to remove modeling artifacts or to make the contributing areas more consistent with site-specific hydrologic features or streamflow data. The data series report (Carlson and others, 2017; refer to the section below) associated with this data release describes the process used to create the USGS groundwater-contributing areas and this data release serves to publish those model results in their original format in a single, publicly accessible publication. This data release contains shapefiles of groundwater-contributing areas and the outline of each model area in the following folders available for downloading: 'LowerCape' 'Monomoy' 'PlyCar' 'Sagamore' ‘Ancillary’. The shapefiles in these folders are aggregated in an ArcMap project, "USGS_original_contributing_areas_PlyCar_CapeCod_shapefiles.mxd", which is included in this data release and organizes the shapefiles for all groundwater-contributing areas for each model area for the Plymouth-Carver region and Cape Cod. A readme.txt file is also included that describes the file folders associated with each model area. These groundwater-contributing areas are associated with the following publications: Carlson, C.S., Masterson, J.P., Walter, D.A., and Barbaro, J.R., 2017, Development of simulated groundwater-contributing areas to selected streams, ponds, coastal water bodies, and production wells in the Plymouth-Carver region and Cape Cod, Massachusetts: U.S. Geological Survey Data Series 1074, 17 p. [Also available at https://doi.org/10.3133/ds1074.] Masterson, J.P., Carlson, C.S., and Walter, D.A., 2009, Hydrogeology and simulation of groundwater flow in the Plymouth-Carver-Kingston-Duxbury aquifer system, southeastern Massachusetts: U.S. Geological Survey Scientific Investigations Report 2009–5063, 110 p. [Also available at http://pubs.er.usgs.gov/publication/sir20095063.] Walter, D.A., and Whealan, A.T., 2005, Simulated water sources and effects of pumping on surface and ground water, Sagamore and Monomoy flow lenses, Cape Cod, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2004-5181, 85 p. [Also available at http://pubs.usgs.gov/sir/2004/5181/]. Masterson, J.P., 2004, Simulated interaction between freshwater and saltwater and effects of ground-water pumping and sea-level change, Lower Cape Cod aquifer system, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2004-5014, 78 p. [Also available at http://pubs.usgs.gov/sir/2004/5014/].