The Black Hills of South Dakota contains approximately 1,307 miles of streams that support a variety of warm and cold-water fisheries, provide drinking water for local communities, and are used for recreational activities like fishing, swimming, and kayaking. In the Upper Cheyenne and Belle Fourche River basins, there are decades of water quality data, with records at some monitoring stations starting in the 1970s. The South Dakota Department of Agriculture and Natural Resources collected water quality data for multiple projects throughout the duration of record. Over the years, data was used to assess water quality as required under the federal Clean Water Act (CWA). The CWA aims to determine if waterbodies are supporting their assigned water quality criteria. If they are not, they are identified as impaired and placed on the state’s 303(d) list, which is a list of impaired waterbodies published every two years. These assessments are limited in their ability to track long-term trends in water quality. It is important to know how water quality changes over time to determine how it can best be preserved for future generations and allows for potential degradation in water quality to be noticed before a waterbody is fully impaired. We seek to build on previous efforts to examine long-term water quality trends in the region by analyzing additional parameters, including phosphorus, nitrogen, total suspended solids, pH, temperature, and bacterial contamination indicators, across the duration of available records. High use streams and those used for domestic water supply will be prioritized, such as Rapid Creek, Spearfish Creek, and the Belle Fourche River. Changes in water quality in the Black Hills (degradation or improvement) over time will be analyzed and will provide critical information to support decision-making by stakeholders and guide future management and conservation efforts.