In 1868, Lexington agreed to accept Maria Hastings Cary's gift of $1,000 and to meet the challenge of matching that sum and providing annual support for a library. With Mrs. Cary's direction, a Board of Trustees was organized consisting of Lexington's Selectmen, School Committee Members, and "settled clergy."

Today, the Trustees elect a five-member Executive Committee to oversee the financial and day-to-day operations of the Library. An Advisory Committee of Lexington residents provides the Trustees with citizen input on a variety of matters. The Executive Committee appoints Advisory Committee members who serve for one-year appointments.