"Collects letters, some of which appear as full-size facsimiles, written over the centuries to America's first ladies by ordinary citizens and famous figures, ..."
Suggested terms to look for include - diary, diaries, letters, papers, documents, documentary or correspondence.
Combine these these terms with the event or person you are researching. (example: civil war diary)
Also search by subject for specific people and events, then scan the titles for those keywords or others such as memoirs, autobiography, report, or personal narratives.
Off campus access instructions (for e-books)
America's First Ladies by 
Dear First Lady by 
Upstairs at the White House; My Life with the First Ladies by