The Ames Free Library first opened its doors in 1883. Under the terms of the will of Oliver Ames II, $50,000, in trust, was left for the construction and support of a Library for the benefit of the inhabitants of Easton MA. Fifteen thousand dollars of this amount was designated for a permanent fund, the income of which shall be devoted to increasing the library and keeping the building, its appurtenances, and contents in repair. This fund was added to by his descendants through the years and constituted its sole support until 1972 when town support was given in order to qualify the library for state aid.

The main building was designed by Henry Hobson Richardson in 1877 and opened in 1883. One of the outstanding men in the history of American architecture, Richardson was the teacher of Louis Sullivan, the father of the modern skyscraper, whose pupil, Frank Lloyd Wright remains one of the foremost architects of this century. The Ames Free Library is one of four public libraries in Massachusetts designed by Richardson. The others are located in Malden, Quincy, and Woburn.
The library is built of Milford granite with the same Longmeadow trim used on Trinity Church in Boston. The very low cavernous arch over the doorway was used here by Richardson for the first time and became one of the most prominent and widely imitated characteristics of his style.

The picturesque carvings and corner gargoyles on the outside of the building are the design of Stanford White as is much of the interior wood detail, including the unusual barrel-vaulted ceiling in the book stack wing. The ceiling is butternut wood. White also designed the ornately carved mantelpiece of Portland stone in the reading room which bears the handsome bronze relief of Oliver Ames II, by Augustus St. Gaudens.

Renewed interest in Richardson's work has resulted in students from all over the country and abroad coming to study and examine this finely preserved example of his work.

The children's wing, built in 1931, was the gift of Mrs. William H. Ames (Fanny Holt Ames), a member of the Board of Trustees for 40 years, in memory of her husband William Hadwen Ames. The addition was designed by Shepley, Rutan, and Coolidge of Boston, the architectural firm formed by three members of H.H. Richardson's office upon his death in 1886.

In February of 1998, the library received a large gift from the estate of Fanny Holt Ames in order to increase the endowment funds of the library to benefit the school children of Easton.