Bathymetry for Mississippi Sound was derived from thirty-three surveys containing 371,210 soundings. Five overlapping, older, less accurate surveys were omitted before tinning. The average distance between soundings was 89 meters. The thirty-three surveys used dated from 1960 to 1979. The range of soundings for the surveys used was 0.8 meters to -17.6 meters at mean low water. A mean high water value of 0.5 meters was assigned to the shoreline. Twenty-five points were found that were not consistent with the surrounding points. These were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676). Mississippi Sound has forty-four 7.5 minute DEMs and three one degree DEMs. The 1 degree DEMs were generated from the higher resolution 7.5 minute DEMs which covered the estuary. A Digital Elevation Model (DEM) contains a series of elevations ordered from south to north with the order of the columns from west to east. The DEM is formatted as one ASCII header record (A- record), followed by a series of profile records (B- records) each of which include a short B-record header followed by a series of ASCII integer elevations (typically in units of 1 centimeter) per each profile. The last physical record of the DEM is an accuracy record (C-record). The 7.5-minute DEM (30- by 30-m data spacing) is cast on the Universal Transverse Mercator (UTM) projection. It provides coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as a standard USGS 7.5-minute quadrangle but the DEM contains over edge data. Coverage is available for many estuaries of the contiguous United States but is not complete.