The name Mill Hill East came about in 1935, only slightly before the railway was electrified as a part of London Transport's Northern Line in 1939. Originally the area was called Bittacy Hill.
Bittacy House and farm were the main estates until the 1860s. The farm was halfway down opposite Saunders Lane and continued as a farm until 1908. The first developments started in the 1860s. The North Middlesex Gas Company Works were opened in 1862 and continued until it was demolished in 2000 and replaced by Waitrose. In 1865 more than a hundred navvies and brick makers arrived to build a viaduct across the Dollis for the new railway. The navvies had a camp near to the Dollis with a small chapel. Mill Hill Station opened in 1867.
In a triangle formed by Bittacy Hill, the railway and Saunders Lane, a small community evolved in houses built for railway and gas workers along Murray Road, Station Villas and the south side of Saunders Lane. By the 1890s on either side of the Railway Hotel (present building c1905) there were a couple of shops, including a fishmongers and general stores, and a mission hall with a chapel school. This can be regarded as the original centre of Mill Hill East. The council built maisonettes north of Saunders Lane (c1932).
Mill Hill Barracks (latter Inglis Barracks) was the home of the Middlesex Regiment (the 'Die-Hards') from 1905 to 1961. It was also used by The Royal Electrical and Mechanical Engineers (REME) from 1943, and the Home Postal Depot (now the British Forces Post Office) from 1962. During the 1960s and 1970s a large number of houses were built as married quarters. In 1988 the Provisional IRA detonated a bomb at the barracks killing Lance Corporal Robins.
North of the barracks the German firm of Carl Zeiss built an optical works in 1912, which was closed during the First World War, but reopened around 1919 as the United Kingdom Optical Co Ltd. In 1988 the International Bible Students Association, associated with Watchtower House, took over the site. Bittacy house was demolished in 1950 and Watchtower house was built on the site in 1955 (formally opened 1958). Here the Jehovahs Witness periodicals Awake and Watchtower are produced in 25 languages for 55 countries. In 2002 120 million magazines were produced.