The buildings, although architecturally different, are predominantly made out of locally quarried granite, and their grounds are landscaped in similar ways.

The building was enlarged in the 1860s by architect Gridley J. F. Bryant, and again in 1909-10 by Edward Dow of Peabody & Stearns.

The three-story granite building is topped by a gilded dome rising to a height of 149 feet (45 m).

[2] The grounds of the State House include statues of figures important in state history: Daniel Webster, John Stark, Franklin Pierce, George H. Perkins, and John P. Hale are all represented by bronze statues.

Architecturally, the building is roughly in a Chateau style, with Late Gothic and Renaissance Revival details.