It would be 46 more years before the 19th Amendment guaranteed women the right to vote. The letter, saved by Hooker, ended up stashed in a wooden box along with nearly a hundred others relating to the suffrage struggle. And there they sat for more than a century, unknown to historians or seemingly anyone else.

Now, the letters have been acquired by the University of Rochester as part of a larger trove of material that some are calling the biggest discovery of its kind in decades.

“It’s a stunning collection,” said Ann D. Gordon, a retired professor at Rutgers University and the editor of the Elizabeth Cady Stanton and Susan B. Anthony Papers Project. “That it’s being delivered all in one piece, with such a clear provenance, is remarkable.”

The collection, which Ms. Gordon is so far the only outside scholar to see, includes 26 letters from Anthony, 10 from Stanton and dozens from other suffragists. There are also broadsides, pamphlets, newspaper clippings and other material that Hooker kept in a kind of circulating library, many with “I.B. Hooker, please return” marked in her handwriting.