The short-lived intermediate daughter isotopes of the U-decay series have proven to be important tracers of the nature and time scales of recent Earth processes. Current applications of these isotopes range widely from Quaternary geochronology to groundwater hydrology to ocean chemistry to magmatic processes beneath active volcanoes. One of the most important laboratory tools for these measurements is a high-purity Th-229 isotopic tracer, which is used both to determine the abundance of Th and, often, the Th isotope ratio of a sample by mass spectrometry. Unfortunately, there is no commercially available supply of high-purity Th-229 that will meet the current and future demands of the U-series isotope research community. This project secured a long-term source of high-purity Th-229 for U.S. researchers in this field through collaboration with the scientific staff of the Oak Ridge National Laboratory. The research conducted using this new high-purity Th-229 tracer will include diverse topics of unambiguous benefit to society, such as understanding climate and sea level change during the late Quaternary, deciphering magmatic processes at active volcanoes, evaluating potential sites for long-term storage of radioactive waste, and characterizing the transport of radionuclides in groundwater. The purity of the Th-229 tracer used by these researchers has a profound impact upon data quality, and thus, the outcome of projects such as these. This is an issue of particular importance for the future potential of measurements using plasma ionization mass spectrometry, which makes it possible to push the limits of accuracy and precision for U-series isotopic analyses of geological materials. Ultimately, this project will also promote the ability of these researchers to teach and train undergraduate and, especially, graduate students in the field of geochemistry. U.S. researchers in the field of U-series isotope geochemistry may request an aliquot of the high-purity Th-229 by sending a completed application (click here) to the chair of the committee (currently Dr. Aaron J. Pietruszka).