Italian Renaissance features and rock-faced granite create a strong public presence for Montpelier's library. Two stories with large windows and a capping entablature are topped by an attic with elliptical windows and a projecting modillioned cornice. Advancing slightly, a centered entrance pavilion has paired colossal pilasters that frame a double loggia, trabeated below and Palladian above, carried on pink granite columns and crowned by a balustrade. On its south facade, the cornice wraps around a curving, two-story bay. The interior has oak and marble wainscoting, staircases, and fireplaces and a skylit second floor. Montpelier resident John E. Hubbard paid for the library, partially with funds willed for a library by his aunt and uncle, Martin M. and Fanny Kellogg of New York City, who were both Montpelier natives. An exquisite application of Vermont granite, the library heralds the ascendancy of Beaux-Arts classicism for the design of civic buildings over the next several decades.
A flood in 1992 that severely damaged the basement-level children's room and a bequest in 1997 precipitated an interior restoration and major expansion in 2001. The contemporary addition (cited for design excellence in 2004 by the Vermont Chapter of the AIA) echoes in an abstracted form major design elements of the original building—basement, cornice, coursing patterns, bay window—and introduces natural wood to warm the facade adjacent to a south-facing reading court.