9, Grosvenor Square W1

No. 9 Grosvenor Square is a corner terraced town house built around 1725 by William Barlow, junior, a bricklayer. The building has undergone some alterations in the early to mid-19th century and further changes internally in the early 20th century. It features a brown brick façade with a banded stucco ground floor and a slate roof. The house stands three storeys high, with a basement and a dormered mansard, and is three windows wide.

On the right side of the ground floor, there is a protruding stucco corridor that runs along the flank of the adjoining No. 88 Brook Street, ending in an angled antae porch, likely a modification from the early 19th century. The upper floors have recessed sash windows with intact glazing bars, set in stucco reveals with red brick dressings and under cambered gauged arches, along with blind boxes on the first floor. The building has a parapet with coping and a cast iron balcony on the first floor. The return side features an irregular three-window arrangement with chimney stacks and wrought iron area railings.

Inside, the house mostly retains early to later 19th-century decoration, including an oval top-lit rear chamber on the ground floor. Notably, this house was the residence of John Adams, the first U.S. Ambassador to the Court of St. James's from 1785 to 1788. It is one of only four houses that survived the mid-20th century redevelopment of the square and is the only one to have substantially retained its original exterior.