The Thornhill Estate was laid out by estate surveyor Joseph Kay and a number of speculative builders from 1846 to 1852 on land which had been mostly used for dairy farming. Thornhill Square, the largest square in Islington, dates from 1847. Early residents of the square were well-off professionals and the garden was originally private. The railings, which date from 1852, survived WW2, but the area had declined and in 1946 Captain Noel Thornhill gave the gardens to the council for public use. They were newly laid out in 1953 as part of Coronation Year improvements.
Thornhill Crescent was begun in 1849. St Andrew's Church (1852-54) was built at a cost of £6,500 by Francis B Newman and John Johnson, whose design won a competition to build it.