Over a century of mining in northern Idaho’s Silver Valley has led to widespread metals contamination in the Coeur d’Alene River watershed, resulting in its designation as a Superfund site and extensive remediation efforts. The U.S. Geological Survey (USGS), in collaboration with the Environmental Protection Agency (EPA), has collected surface water quality data for over 35 years to guide remediation and assess environmental changes. Key contaminants include mining-related lead and zinc. Long-term trend analysis reveals significant declines in lead and zinc concentrations, especially in the upper watershed, though the lower watershed remains a source of lead. In addition, phosphorus data offers insights into dynamic watershed processes affecting nutrient delivery to Coeur d’Alene Lake. This long-term dataset indicates that remedial actions have improved water quality in the watershed while also pointing to areas for future work.