This dataset is in support of the publication "The addition of 144Nd to routine ICP-MS analysis as a quick screening tool for approximating earth elements (Q-STAR) in natural waters". It contains inductively coupled plasma mass spectrometry (ICP-MS) data from samples analyzed at the National Water Quality Laboratory (NWQL) from April 2021-May 2022. Data listed include estimated neodymium (Nd) concentrations and site numbers.Site numbers can be used to search published USGS data bases such as the National Water Information System (NWIS) for previously published sample information and is shown here to highlight unpublished estimated Nd concentrations from this work. A set of archived samples from NWQL analyses were quantitatively measured for rare earth elements at both the Army Corps of Engineers Engineering Research and Development Center Environmental Laboratory (ERDC-EL) in Vicksburg, MS and the USGS Boulder Common Services Lab in Boulder, CO (BCSL) using ICP-MS. Dissolved organic carbon (DOC) concentrations were available for a subset of archived samples and were analyzed at NWQL. Finally, samples collected from Colorado Springs, CO, Estes Park, CO and Leland, MS were analyzed for rare earth elements using ICP-MS.