The original structure was a 2-story building that has been enlarged and encased by a number of rennovation projects over the years. The dome was added in 1889 after a fire. 

The building is shaped like a sideways H, with a golden dome over the cross-bar of the H and with a long wing extending westward towards the Delaware River. To the rear of the building, a number of architecturally dissimilar, unusually-shaped additions have been added, which were later subject to attempts at renovation in order to match the style of the original wing. The State House is set not on a park-like campus, as are many state houses, rather it is integrated into an urban setting along historic State Street and is surrounded by other legislative buildings. The most scenic view of the building is from the west, near the Delaware River, which is the side dominated by the various additions. Viewed from the front on State Street, the dome is scarcely visible and there is little sense of the scale or design of the building. The current Office of the Governor section in the complex occupies the remaining portion of the original 1792 State House.