Founded in 1731, this is one of the oldest cultural institutions in the United States and the only major Colonial American library that has survived virtually intact, despite having moved from building to building. From 1774 to 1800 it functioned as the de facto Library of Congress, and until the late 19th century it was the city library. Ten signers of the Declaration of Independence were members, among them Benjamin Franklin, Robert Morris, Benjamin Rush, and Thomas McKean. The 500,000-volume collection includes 200,000 rare books. Among the first editions—many acquired when they were first published—are Herman Melville's Moby-Dick and Walt Whitman's Leaves of Grass. The library is particularly rich in Americana up to 1880, black history to 1915, the history of science, and women's history. Changing exhibits showcase the library's holdings.