The U.S. Geological Survey (USGS), in cooperation with the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration (NOAA), has conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary (SBNMS) region since 1993. The interpretive datasets and source information presented here are for quadrangle 5, which is one of 18 similarly sized segments of the 3,700 square kilometer (km2) SBNMS region. The seabed of the SBNMS region is a glaciated terrain that is topographically and texturally diverse. Quadrangle 5 includes the shallow, rippled, coarse-grained sandy crest and upper eastern and western flanks of southern Stellwagen Bank, its fine-grained sandy lower western flank, and the muddy seabed in Stellwagen Basin. Water depths range from <25 m on the bank crest to ~100 m in the basin. The data presented here for quadrangle 5 are the foundation for Scientific Investigations Map 3515 (Valentine and Cross, 2024), which presents maps of seabed topography, ruggedness, backscatter intensity, distribution of geologic substrates, sediment mobility, distribution of fine- and coarse-grained sand, and substrate mud content. The maps of quadrangle 5 show the distribution of substrates across the southern part of Stellwagen Bank and the adjacent basins. Bathymetric and seabed backscatter imagery, photographs, video, and grain-size analyses were used to create the geologic interpretations presented here and have been reprocessed and released in segments to supports these interpretations. For the quadrangle 5 interpretations, data from 729 stations were analyzed, including 620 sediment samples. The seabed geology map of quadrangle 5 shows the distribution of 20 substrate types ranging from boulder ridges to mobile and rippled sand, to mud. Substrate types are defined or inferred through sediment grain-size composition, surface morphology, sediment layering, the mobility or immobility of substrate surfaces, and water depth range. Scientific Investigations Map 3515 portrays the major geological elements (substrates, topographic features, processes) of environments within quadrangle 5. It is intended to be a basis for the study of sediment transport processes that affect a shallow, offshore bank, for the study of the ecological requirements of invertebrate and vertebrate species that use these substrates, and to support seabed management in the region.