The Watkinson Library was founded in 1858 under the provisions of the will of David Watkinson, an English-born Hartford merchant and a founding trustee of Trinity College. Watkinson wanted Hartford to have a “Library of Reference, accessible at all reasonable hours and times to all citizens and other residents and visitors in the State of Connecticut under such controls, rules and regulations … as will best secure the preservation of the books … and comport with the general convenience.” To establish his “Library of Reference” he willed a sum of $100,000 for general endowment.
The Library opened in 1866 in the Wadsworth Atheneum with 12,000 volumes on its shelves under the supervision of a distinguished board of trustees, including George Brinley, a pioneer collector of Americana, and the prominent educator Henry Barnard. The first librarian was James Hammond Trumbull, who was Connecticut's first State Librarian and later was Secretary of State for Connecticut during the Civil War period. A true polymath, famed as an outstanding bibliographer of Americana and a leading scholar of American Indian languages, Trumbull served from 1863 until his retirement in 1891. The range and excellence of the Watkinson’s collections are due in no small part to the great learning of Trumbull, who was once described by Mark Twain as “probably the richest man in America in the matter of knowledge.” Trumbull trained his successor, Frank Butler Gay, who served until 1934, and for a span of over 70 years these two directed the growth of the Watkinson to a scholarly collection of 130,000 volumes in the humanities.
In the mid-20th century, financial pressures led the Watkinson trustees to seek another institution with which to affiliate, and in 1952 the Library became a part of the Trinity College Library system. A unique feature of this union is that by charter the Watkinson Library maintains a distinct identity as a separate, non-circulating collection available to the needs of all researchers, not only those in the Trinity College community. The Watkinson's collections were first housed at Trinity on the top floor of the library building newly constructed in 1952. In 1979, the Library was moved to its current location on the A-Floor in the first addition to the 1952 building. This space was completely renovated in 2007.