These are primary source databases that focus on Black Americans, but we do also have primary source databases that are more broadly about US history. See my US History Research Guide for a list of those.
Use the Library Catalog to find books. Be sure to pay attention to the date and publisher of the book - the Catalog does include older materials and primary sources.
Use these databases to find articles from scholarly journals. Scholarly journals also have features like book reviews, so make sure it's a research article.