The line was opened as the Central London Railway in 1900, crossing central London on an east–west axis, as the third deep-level Tube line to be built after electric trains made them possible. It was later extended to the western suburb of Ealing. After the Second World War, the line was expanded considerably into the recently constructed suburbs, taking over steam-hauled outer-suburban routes to the borders of London and beyond to the east. This realised plans that had been delayed by the war, when construction stopped and the unused tunnels were used as air-raid shelters and factories. However, suburban growth proved to be less than expected, and of the planned expansions one (to , Buckinghamshire) was cut short due to its location in the Metropolitan Green Belt and another (to ) ultimately closed in 1994 due to low patronage; the section between Epping and Ongar later became part of the Epping Ongar Railway. The Central line has mostly been operated by automatic train operation since a major refurbishment in the 1990s, although all trains still carry drivers. Many of its stations are of historic interest, from turn-of-the-century Central London Railway buildings in west London to post-war modernist designs on the West Ruislip and Hainault branches, as well as Victorian-era Eastern Counties Railway and Great Eastern Railway buildings east of , from when the line to Epping was a rural branch line.