The U.S. Geological Survey (USGS) undertook a 5-year study beginning in 2016 to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border to the western part of the panhandle of Florida; these aquifers are collectively referred to as the coastal lowlands aquifer system. This study is one of several regional groundwater availability studies being done as part of the USGS Water Availability and Use Science Program. Groundwater from the coastal lowlands aquifer system is used mainly for public, irrigation, and industrial supply. Land-surface subsidence related to groundwater pumping is an issue of ongoing concern within this study area. During the first two years of the study, the team developed an updated conceptual model of the hydrogeologic framework of the aquifer system, which lead to initial estimates of major water budget components such as recharge, surface-water/groundwater exchange, and coastal discharge. This data release documents the hydrogeologic data that were compiled and used to define the hydrogeologic framework.