In cooperation with the Llano Estacado Underground Water Conservation District (LEUWCD), the Sandy Land Underground Water Conservation District (SLUWCD), and the South Plains Underground Water Conservation District (SPUWCD), the U.S. Geological Survey (USGS) compiled historical geophysical and geochemical data in Gaines, Yoakum, and Terry Counties, Texas, and collected additional data where gaps were evident to assist with building a conceptual hydrogeologic model of the Gaines, Yoakum, and Terry Counties region. The compiled historical data includes all data available from predevelopment (pre-1945) through present day. For this study, predevelopment is considered everything prior to 1945 when the large-scale groundwater extractions for agricultural purposes started. The use of center pivot irrigation and the adaptation of automotive engines for groundwater wells had a large impact on the regional groundwater system around 1945. The compiled historical data included well-construction information, previously measured water level and water quality data, and hydraulic-properties testing data (slug tests, aquifer tests, pump tests, and so forth.). Additionally, the USGS collected surface time-domain electromagnetic soundings, borehole geophysical logs, and water-quality samples to develop and refine the hydrogeologic framework of the area. This data release includes all of the compiled historical water-level and water quality data, as well as geophysical data collected for the study.