The easternmost section of Riding House Street was previously known as Union Street.
Riding House Street (previously called Riding House Lane) extended west from Edward Street only as far east as Great Titchfield Street. East of Great Titchfield Street this was Union Street, which became part of Riding House Street in 1937.
The name Union Street dates from 1764 and reflects an accord between the Portland and Berners Estates, whose boundary line the street followed. Its layout dates from 1759 or so.