The Salem Athenaeum was founded in 1810 through the merger of two smaller private libraries in Salem – the Social Library and the Philosophical Library.

The Social Library was founded by members of the "Monday Evening Club" in 1760. The members consisted primarily of a young group of merchants, including Samuel Barton, Joseph Bowditch, Richard Derby Jr., Benjamin Pickman, John Nutting Jr., and William Vans. There were also several clergymen who were early members: William McGilchrist, Thomas Barnard, and William Walter. The membership was not restricted and there were few rules. At the beginning, a share cost $11. The library was originally housed in a brick schoolhouse (located where the courthouse now stands) and was later moved in 1785 to the Central Building on Central Street.

The Philosophical Library, founded in 1781, was established by the Reverend Joseph Willard (of Beverly, Massachusetts) along with Reverend Manasseh Cutler, Revered John Prince, and Reverend William Bentley. The original volumes (205) of the library came as a result of the Cabot's privateer Pilgrim which captured the ship Mars off the Irish Channel. On board were the books of a distinguished scientist Dr. Richard Kirwan which were being sent to Quebec. The Salem clergymen bought the books at auction for the Philosophical Library. It should be noted that Dr. Kirwan was later offered compensation but refused since he felt the books were being put to good use. The Philosophical Library had stricter rules than the Social Library: members could live no further than six miles from the Beverly Ferry and a maximum of four books could be borrowed for a three-month period. At the outset the shares cost $45.

In 1810 the proprietors of the Social and Philosophical Libraries decided to merge and enlarge. Dr. Holyoke gained a charter from the governor and on March 12, 1810 the Salem Athenaeum became a corporation. The shares were limited to 100 and sold for $100 each. The shareholder was given the privilege of the use of the Athenaeum. Those who were members of either of the previous libraries had their shares valued at $50 each, and members of both were given a share in the Athenaeum without an additional fee. In 1845, after the Athenaeum had moved several times, it gained a permanent home when Caroline Plummer left $30,000 for a new building. By 1857 Plummer Hall, located at 132 Essex Street, was completed and occupied.

The Salem Athenaeum's book collection encompassed a wide range of topics: geography, history, philosophy, biography, science, and theology. There were also collections of books on art, poetry, fiction, foreign literature, and novels as well as periodicals. The library, which contained about 51,000 volumes, became a center for scholarly research and investigation. Although the Athenaeum had only one hundred shareholders, it had about a thousand or more users, for each shareholder usually represented a family. The Athenaeum was used by such noted Essex County residents as Nathaniel Hawthorne and Nathaniel Bowditch.

The Essex Institute occupied the lower floors of Plummer Hall, and its members were allowed to use the Athenaeum library. In return, the Institute paid $300 annually as well as half of the heating costs, and the proprietors of the Athenaeum were allowed to consult the books in the Institute's library. By 1905 the use of the Athenaeum had decreased so that its proprietors sold Plummer Hall to the Essex Institute for $50,000. A new library "Homewood", located at 337 Essex Street, was completed in 1907 and is the home of the Athenaeum today.