While PFAS compounds are believed to be ubiquitous in U.S. waterways, no nationwide surface water quality survey exists. As a result, the levels and effects of PFAS are unknown for many rivers, streams, lakes, and other U.S. surface waters that serve as drinking water sources, recreational waters, and fisheries. To address this troubling lack of information about the presence of, and dangers posed by, PFAS in U.S. surface waters, Waterkeeper Alliance contracted with Cyclopure, Inc., a materials science and environmental engineering firm headquartered in Illinois, to help conduct a monitoring project in which we worked with more than 100 Waterkeeper groups across the United States on an unprecedented initiative to test U.S. surface waters for PFAS contamination.