Bottom altitudes of the Mississippi River Valley alluvial aquifer (MRVA) were compiled from interpretations of subsurface geophysical logs (log picks) at about 10,000 boreholes and wells located throughout the Mississippi Alluvial Plain (MAP) that were available from previous investigations. Five sources of the bottom altitude data are listed numerically in the Cross Reference section (below) and correspond with the Ref_code listed in the .shp dataset. Borehole geophysical data (log picks) were referenced (corrected) to the National Elevation Dataset (NED) 10-meter digital elevation model (DEM; https://nationalmap.gov/elevation.html). Log picks that required a DEM correction of less than 20 feet were retained for use in a subsequent geostatistical estimation of the MRVA bottom altitude, after additional filtering to remove duplicate log picks yielded a MRVA bottom-altitude dataset of 9,292 data points, described in this data release. Values of MRVA thickness were prepared by subtracting bottom altitudes from DEM values at the data locations. A second filtering of MRVA bottom-altitude data based on results of geostatistical analytical procedures and analysis of updated log picks in the Mississippi Delta region from Cross Reference 3 generated the 6,604-element dataset of MRVA bottom altitude and thickness described in this data release.