The official opening was presided over by President William Howard Taft, with Governor John Dix, and Mayor William Gaynor also present. This was the culmination of exactly 16 years of work, as on May 23, 1895, representatives of the Astor and Lenox Libraries, along with the Trustee of the Samuel Tilden fortune, agreed to merge the libraries, and create "The New York Public Library, Astor, Lenox and Tilden Foundations."
The day after the opening, the Main Branch was opened to the public for the first time.
The building, which was started in May 1902, was designed by architects Carrére and Hastings in the Beaux Arts style. In addition to its imposing design, they also incorporated a system of multiple floors of book stacks, and a means of getting books to library users in a quick and efficient manner. The building was the largest marble structure in the United States as of its opening.