Ask every collection at once.

Discovery mode: your question goes to each participating collection separately, and each answers only from its own records — grouped by collection, every claim cited. There is no blended answer; the point is finding out what the site holds.

4 of the 6 collections take part here: History of the Negro Race in America, 1619–1880; The Debates in the State Ratifying Conventions, 1787-88; The Federalist Papers; The Frederick Douglass Papers. The Richmond Planet and European Commission answer only on their own shelf.