Historical Statistics of the United States is the standard source for the quantitative facts of American history. HSUS provides data on social, behavioral, humanistic, and natural sciences including history, economics, government, finance, sociology, demography, education, law, natural resources, climate, religion, international migration, and trade - quantitative facts of American History. The fully searchable and downloadable electronic edition permits users to graph individual tables and create customized tables and spreadsheets reflecting their own particular areas of interest.
Since 1995, eHistory has been maintained by The Ohio State University Department of History. The online collection includes primary sources, multimedia, book reviews, timelines, and many other sources of historical importance.
Want an example of the breadth of this collection. Here is one of the primary sources that was highlighted when I visited the site.
No serious study of the American Civil War is complete without consulting the Official Records. Affectionately known as the "OR", the 128 volumes of the Official Records provide the most comprehensive, authoritative, and voluminous reference on Civil War operations.