As one of the best-maintained surviving Georgian public buildings in the United States from the colonial era, it was designated a National Historic Landmark (NHL) in 1960.

The two-and-a-half-story seven-bay front facade looks down the square to the similar Brick Market (now the Museum of Newport History), another NHL.

By putting the home of the colonial assembly at the top of the Parade (as Washington Square was then known), the town's leadership hoped to create a public space similar to that found in the English cities they or their parents had emigrated from.

[2] Architect Richard Munday's design, one of his last, emulates Christopher Wren's buildings on the exterior but incorporates an interior layout similar to that of English town or guild halls.

Three years later, the inaugural board meeting of the Corporation of the College in the English Colony of Rhode Island, which became Brown University, took place in the building.

[2][6] Tensions between the colonies and Britain continued to grow, leading to the Gaspée Affair of 1772, in which a ship of the Royal Navy was burned off present-day Warwick by colonists resisting the enforcement of the Navigation Acts.

[7] Although it could have sent any suspects to London to face trial before an Admiralty court, a provision which greatly concerned most colonists, it found insufficient evidence to prosecute anyone.

It is widely believed that a French Army chaplain celebrated Rhode Island's first Roman Catholic Mass at Colony House during this period, but no evidence has been found of this.

After the surrender at Yorktown, in 1782, Rochambeau held a banquet in the building's first-floor Great Hall to honor George Washington.

[2] In 1786 Trevett v. Weeden one of the earliest cases of judicial review was decided in the building by the Rhode Island Supreme Court.

[2] In 1900, with Rhode Island's current capitol building mostly complete, the legislature ended its tradition of alternating sessions between the state's two largest cities.

Newport's well-preserved historic character drew Steven Spielberg to the city in 1997, where it stood in for mid-19th century New Haven, Connecticut, during principal photography for Amistad.