Belsize Manor was built by Daniel O'Neill for his wife, the Countess of Chesterfield, in the 17th century. Urbanisation took place largely between 1852 and 1878, by which time it extended to Haverstock Hill. After World War I, the construction of blocks of flats began, and now a great many of the larger houses are also converted into flats.

Belsize Park underground station was opened on 22 June 1907 by the Charing Cross, Euston & Hampstead Railway as an intermediate station on its line from Charing Cross to Hampstead. It is served by three lifts and there are 219 steps. The station was designed by Leslie Green and has his familiar facade of ox-blood faience with four round arched windows. It remained largely untouched until the late 1980s when the lifts were replaced and a new ticketing system installed.

It was during the 1930s that Belsize Park contributed most to the artistic and intellectual life of Hampstead. Artists associated with the Mall studios included Dame Barbara Hepworth from 1927 to 1939, her first husband John Skeaping and second Ben Nicholson from 1931 to 1939, and Henry Moore, who lived at no. 11A Parkhill Road from 1929 to 1940. They were members of Unit One, a group of artists and architects founded in 1933 by Paul Nash (1889-1946), who lived at no. 3 Eldon Grove from 1936 to 1939. Sir Herbert Read, the poet and art critic, who lived in 1934-5 at the Mall studios, which he described as a 'nest of gentle artists', published the group's manifesto, a theory of modern style.

Another centre was no. 37 Belsize Park Gardens, meeting place of MARS, an architectural group, and home of Jack Pritchard, who founded Isokon, a firm making modern furniture designed by people like Walter Gropius and Marcel Breuer, refugees who brought a European dimension to the abstract design movement in the arts. Others included Piet Mondrian, the Dutch painter, who stayed with the Pritchards before moving to no. 60 Parkhill Road (1938-41). Pritchard also commissioned Wells Coates in 1934 to build the Isokon or Lawn Road flats, partly to house artistic refugees, on a site which he owned. Built in concrete in a functional style, the flats came to be recognized as 'a milestone in the introduction of the modern idiom into London'.

In World War II, a large underground air-raid shelter was built here and its entrance can still be seen near the tube station at Downside Crescent. The area on Haverstock Hill north of Belsize Park underground station up to Hampstead Town Hall and including part of a primary school near the Royal Free Hospital was heavily bombed.

Belsize Park these days is a lively area with many restaurants, pubs and cafés along Haverstock Hill and also England's Lane.

Glossary: A History of the County of Middlesex: Volume 9, edited by C R Elrington.