Earlham College Director of Special Collections Tom Hamm provides this overview of the Friends Collection:

The Friends Collection is one of the three or four best collections of Quaker materials in North America, and one of the five or six best in the world. From  a foundation of 400 Quaker books and pamphlets (350 of which are still in the collection) donated by English Friends when Earlham opened as Friends Boarding School in 1847, we have grown to a collection of about 13,000 catalogued books, thousands of pamphlets, and several hundred manuscript collections. Simply put, there is almost no significant published Quaker work that we do not have in some form, whether it is an original, a photocopy, a microfilm, or, increasingly, on-line access. We are the one part of the Earlham libraries that collects published materials comprehensively—we try to acquire a copy of any book, pamphlet, or periodical, published by or about Friends, anywhere in the world, in any language.

You can read more from Tom here: http://esrquaker.blogspot.com/2013/09/the-earlham-friends-collectio...