Technical Abstract: The USDA-ARS water resources program has developed a web-based data system, STEWARDS: Sustaining the Earth’s Watersheds, Agricultural Research Data System to support research that encompasses a broad range of topics such as water quality, hydrology, conservation, land use, and soils. The data system contains data from long-term watershed research projects, currently from 1955 to 2010 with variable temporal coverage across sites and variables within sites. In March, 2011, data from watersheds in Georgia, Iowa, Indiana, Maryland, Missouri, Mississippi, Ohio, Oklahoma, Pennsylvania, and Texas are available and additional watersheds are preparing data for inclusion. The data are not real-time, instead archiving data following analysis and publication by the research team, with approximately annual updates. The data sets include comprehensive descriptive files and metadata and are available for download as zip files, with spreadsheets, GIS files, and associated metadata and descriptive files. The primary users are ARS and university researchers addressing a multitude of research questions with a variety of simulation models. There is the potential for diverse research applications to address watershed scale questions in single or multiple watersheds from key agricultural regions from around the USA. The data are limited for national assessments, because the data are highly heterogeneous across watersheds and across time. However, this is a unique data source for developing and testing models that are applicable to local, regional, or national scale assessments of watershed processes in agricultural landscapes.