The United States Geological Survey (USGS) is working cooperatively with the National Oceanic and Atmospheric Administration (NOAA) to interpret the surficial geology in estuaries along the coast of the northeastern United States. The purpose of our present study is to define the sea floor morphology and sedimentary environments in an area of Rhode Island Sound using sidescan-sonar and bathymetric data collected onboard the NOAA Ship RUDE as well as historic seismic-reflection data. The mosaic, bathymetry, and their interpretations serve many purposes, including: (1) defining the geological variability of the sea floor, which is one of the primary controls of benthic habitat diversity; (2) improving our understanding of the processes that control the distribution and transport of bottom sediments and their distribution of benthic habitats and associated infaunal community structures; and (3) providing a detailed framework for future research, monitoring, and management activities. The sidescan-sonar mosaics and bathymetry images also serve as base maps for subsequent sedimentological, geochemical, and biological observations, because precise information on environmental setting is important for selection of sampling sites and for accurate interpretations of point measurements.