Justin Winsor, Charles Ammi Cutter, Samuel Swett Green, James L. Whitney, Melvil Dewey, Fred B. Perkins and Thomas W. Bicknell began the organization in 1876. It began in Philadelphia, but its head office is in Chicago now. Anybody can join, but most of its members are librarians. Most members live and work in the United States. Members from other countries make up about 3.5% of the members.