Presidential libraries are many things.

They’re repositories of the official papers and, in many cases, the personal archives and artifacts of our nation’s chief executives, as well as those of their families, friends, and colleagues in public service. And as the name would suggest, they are also home to vast collections of books, articles, dissertations, monographs, and journals about their subject or the presidency in general. They’re a scholar’s dream for historians, researchers, and students alike. If you’re seeking to understand, say, Harry S. Truman’s diplomacy or Ronald Reagan’s life before politics, a journey to Independence, Mo., or Simi Valley, Calif., is probably obligatory.