Baker, Henry Aaron (1753–1836), architect, was educated at the Dublin Society's school of architectural drawing (1777), winning a silver medal (1779), and was apprenticed to Thomas Ivory (qv). He became (c.1786) assistant to James Gandon (qv), his partner, and clerk of the works to the buildings Gandon designed, notably the Four Courts, Inns Quay, and King's Inns, Henrietta St., Dublin, Baker taking responsibility (c.1808) for the completion of King's Inns (1817).
As master of the Dublin Society's school of architectural drawing (1787–1836), he taught neo-classical principles of design. An able administrator, diligent in carrying out his duties, he argued in 1797 that the more scientific nature of architectural drawing demanded greater attention than other branches of drawing, and was successful in his request for an increase in salary – from £60 to £100 a year – thereby placing architectural teaching on a par with the fine arts. As architectural consultant to the society, he designed its new headquarters in Hawkins St. (1796), providing for the first time purpose-built accommodation, which included classrooms and a gallery designed with a long skylight, which ranked as the finest room for exhibitions in the city and became the most popular venue for art exhibitions in Dublin. He designed the statue gallery and drawing schools at Leinster House (1823–7), which later housed the National College of Art and Design.
He designed the triumphal arch at Bishop's Gate, Derry (1789), and the 100 ft (30.5 m) Pillar of Lloyd (1791); built on a hill near Kells, Co. Meath, it was intended as a beacon. He produced his most significant work as one of the principal architects for the wide streets commissioners (c.1799–c.1816). In 1799 and 1800 his designs for D'Olier St. and Westmoreland St. were approved; as streets designed for shops, they predated similar developments in England by about fifteen years. The five-storey granite buildings of Westmoreland St., with their uniform façade, made innovative use of glass on the ground floor.
Baker was a founding member (1823), secretary (1826–7), professor of architecture (1827–31), and honorary secretary (1831) of the RHA, where he exhibited designs (1826–31). Richard James H. Troy ( fl. 1827–34) exhibited a bust (1831) of Baker at the RHA. Baker served as architect (1833–4) of the grand juries of the city of Dublin. He lived for several years at 112 Mecklenburgh St., Dublin, shared in 1831 with Henry S. Baker (relationship unknown), architect and civil engineer, and from 1835 at 2 Wentworth Pl., Dublin, where he died 4 June 1836 and was buried at St Thomas's church, Dublin. Nothing is known of his family.