This dataset contains groundwater-altitude (GWA) data from wells that were used or considered (indicated by the field USE_2020) to create a potentiometric-surface map for the Mississippi River Valley alluvial aquifer (MRVA) for spring 2020. The GWA data was referenced to the North American Vertical Datum of 1988 (NAVD 88). Most of the wells were measured annually, but some wells were measured more than one time in a year and a small number of wells were measured continuously. GWA data were from wells measured in spring 2020. To best reflect hydrologic conditions in the MRVA, the GWA data used to create the 2020 potentiometric surface would be measured in a short-time frame of days or a week and there would be available data (for example from sets of wells with short-screen (about 5 to 10 feet or 1.5 to 3 meters) installed near the top, in the middle, and near the bottom of the aquifer) to indicate vertical flow components. However, most wells screened in the MRVA were measured before the potentiometric-surface map of the MRVA was planned and therefore the timing of each well's measurement(s) was determined by the needs and schedules of the entities doing the measurements. Also, many of the measured wells had longer screens (from greater than 10 feet or 3 meters and covering a substantial part of the aquifer thickness), therefore their water-level measurements represent an average head in the aquifer for that location. The resultant potentiometric-surface contours and raster represents the generalized central tendency for spring 2020, but it would not be useful for some purposes, such as for calibration of a groundwater-flow model for early April 2020 or for some local scale assessments.