Salt marshes are environmental ecosystems that contribute to coastal landscape resiliency to storms and rising sea level. Ninety percent of mid-Atlantic and New England salt marshes have been impacted by parallel grid ditching that began in the 1920s–40s to control mosquito populations and to provide employment opportunities during the Great Depression (James-Pirri and others, 2009; Kennish, 2001). Continued alteration of salt marsh hydrology has had unintended consequences for salt marsh sustainability and ecosystem services. Great Barnstable Marsh (Barnstable, Cape Cod, Massachusetts) has areas of salt marsh that were ditched as well as natural areas. The U.S. Geological Survey (USGS) measured parameters for groundwater wells (water elevation, water depth below land surface, salinity, and water temperature), soil and air temperature, and other meteorological parameters. All these parameters affect plant productivity and are key components of salt marsh carbon cycling, carbon storage, and its ability to maintain elevation in response to changing sea level. These USGS datasets can be used to evaluate changes in water levels across ditched and natural salt marsh regions and provide information for any future studies of salt marsh productivity and geomorphic models in Great Barnstable Marsh. James-Pirri, M.-J.,Ginsberg, H.S., Erwin,R.m., and Taylor, J., 2009, Effects of open marsh water management on numbers of larval salt marsh mosquitoes: Journal of Medical Entomology, 46(6), 1392-1399, doi:10.1603/033.046.0620. Kennish, M. J., 2001, Coastal salt marsh systems in the U.S.-A Review of Anthropogenic Impacts: Journal of Coastal Research, 17(3), 731-748, https://www.jstor.org/stable/4300224.