This dataset compiles heat flow and temperature gradient data from over 44,000 wells across the United States, along with more than 6,000 related geothermal exploration resources. Originally assembled prior to 2014 for the now-retired National Geothermal Data System (NGDS), the collection aggregates geothermal data collected and curated by the Southern Methodist University (SMU) Geothermal Laboratory and partner organizations. The project was supported by an American Recovery and Reinvestment Act grant from the U.S. Department of Energy, DE-EE0002852, awarded to the SMU Geothermal Laboratory to aggregate heat flow and other relevant geothermal data for sharing across the NGDS. In 2026, the data were moved to the Geothermal Data Repository for open access. SMU Geothermal Laboratory contributed two nationwide heat flow databases to the project. One is based on equilibrium temperature measurements from over 14,000 sites, and the other is based on corrected bottom hole temperature data from oil and gas industry wells from over 30,000 sites. The collection also includes curated well data, scanned field notes, temperature-depth curves, publications, reports, maps, geophysical survey materials, and other supporting documents. Records were corrected, and overlapping sites in the equilibrium heat flow database were linked between the original SMU National database and the UND Global Heat Flow database. Sites that were not previously published because they lacked full heat flow content are included as gradient-only information with detailed temperature data. The dataset is provided as flat-structured downloadable archives with accompanying Excel index files that support filtering by well name, location, description, and related metadata. Data files are labeled with state or institutional origin where available. SMU Geothermal Laboratory grant sub-recipients included Siemens Corporate Technology, a division of Siemens Corporation; the Bureau of Economic Geology, University of Texas at Austin; Cornell Energy Institute, Cornell University; the Geothermal Resources Council; MLKay Technologies; Texas Tech University; and the University of North Dakota. Users should begin with the 01_README and the Excel index files, which provide additional detail on the archive structure, index fields, and how to locate specific data files and related resources within the downloadable zip archives.