The Overbury Collection dates from 1777 to 1963. Materials consist of nineteen hundred rare book editions and nearly one thousand letters and manuscripts by American authors, primarily American women authors. The manuscripts and letters contain material by such authors as Abigail Adams, Louisa May Alcott, Frances Hodgson Burnett, Willa Cather, Helen Keller, Edna St. Vincent Millay, and Gertrude Stein. A few manuscripts and letters given by English professor Eleanor M. Tilton and some by male authors are part of the Collection though their provenance is unclear.

The collection contains catalog cards created by Overbury as well as ones once used by the Library to provide access to the collection and book plates for the book spines that were not used are also included. Personal correspondence and notebooks of Overbury as well as Xerox copies of her correspondence with Seven Gables Bookshop are among the materials.

Clippings collected by Overbury have been cut from the New York Times, New York Herald Tribune, and Saturday Review and occasionally include notes by Overbury or correspondence with dealers. Rare books housed off-site storage include a 1758 edition of poems by Anne Bradstreet, first editions of Fannie Hurst, Eudora Welty, Katherine Anne Porter, and Cornelia Otis Skinner and editions of Phillis Wheatley and Mercy Otis Warren. Books from the Overbury collection that are on-site and available for use can be found in CLIO, the Columbia University Libraries catalog, by searching for "SC05 Overbury": https://clio.columbia.edu/catalog?q=%22SC05+Overbury%22