The Central Sands nitrate and neonicotinoid database consists of over 100,000 measurements of nitrate and neonicotinoid concentrations in groundwater from wells across Adams, Juneau, Marquette, Portage, Waushara, and Wood counties collected between 1953 and 2021. These counties comprise the Central Sands Groundwater County Collaborative (GSGCC), which facilitated the project to gather these data. The purpose of the project was to evaluate trends in nitrate and neonicotinoid concentrations in groundwater and explore correlations between groundwater-quality and land-use type. Findings of this investigation are available in a report published by the Water Resources Institute at UW Madison (https://digital.library.wisc.edu/1711.dl/ASRUSPUU5VR4Q9E).