These datasets consist of a workspace (folder) containing a collection of gridded datasets plus a personal geodatabase containing several vector datasets. These datasets are designed to be used with the ArcHydro Tools, developed by ESRI in partnership with the U.S. Geological Survey, StreamStats Development Team. The datasets, together with the ArcHydro Tools, allow users to delineate watersheds and compute several watershed characteristics. The datasets are distributed in folders named for the 8-digit Hydrologic Unit Code (HUC) each covers. The data structure is the same for each HUC.