Letchworth Museum and Art Gallery was founded in 1914 to house the collections being amassed by the Letchworth and District Naturalists’ Society. The building was designed as a single storey structure by Barry Parker, one of the principal architects of the early Garden City movement. It was enlarged in the 1920s and extended to the rear in 1960-3 to designs by Courtenay Melville Crickmer (who had designed Letchworth Library, next door, in 1938).

Its first curator, W Percival Westell (1874–1943), was a well-known author of works on natural history and archaeology. Appointed as Honorary Curator in 1914, the post became salaried in 1928 and he remained as Curator until his death. During the time spent at the museum, he wrote 84 books and gave 145 radio talks for the BBC, mostly on natural history.He established one of the country’s first museums’ loan services in the 1930s. His assistant in the early 1930s was Erik Shimon Applebaum, later professor of Archaeology at the University of Tel Aviv.

Westell’s successor at the museum was Albert T Clarke, who was in post from 1944 to 1968. His assistant from 1957 was John Moss-Eccardt, who became curator in 1968.

Although run initially by the Letchworth and District Naturalists’ Society, it was transferred to Letchworth Urban District Council in 1939. Since the dissolution of the Urban District Council in 1974, the Museum has been run by North Hertfordshire District Council, together with Hitchin Museum and Art Gallery and, for a few years in the late 1970s and early 1980s, Royston Museum and the First Garden City Heritage Museum.