impressive collection of online resources With a surfeit of online resources for the student of American history, a specialised search engine would be useful. Or a portal devoted to this subject. Perhaps these exist. But as an alternative, you can try this book. Gevinson has expended considerable effort to collect an impressive list of resources.
Each is briefly explained, alongside its URL. Many are freely available. Some are quite specific. Like a collection of maps that has been digitised and put online. Another is a compendium of famous trials, like Scopes or Sacco and Vanzetti. While someone at Stanford put together a collection of dimestore novels and penny dreadfuls that makes fascinating viewing.