Metropolitan District Railway

The Metropolitan District Railway was the predecessor of the District line of the London Underground. Set up on 29 July 1864, at first to complete the "Inner Circle" railway around central London, it was gradually extended into the suburbs. It was a private company that was purchased by the Underground Electric Railways Company of London and moved into public ownership in 1933 as part of the undertakings of the London Passenger Transport Board.

Line openings
The core section of the District commenced at the MetR's South Kensington station and extended in stages to Mansion House. Sections were opened as follows with the District also running westwards over the MetR's tracks to Gloucester Road and High Street Kensington: From this core, the District began extending branches to reach new population centres, mainly in the west:
 * 24 December 1868: South Kensington to Westminster.
 * 30 May 1870: Westminster to Blackfriars.
 * 12 April 1869: Gloucester Road to West Brompton (Earl's Court was opened on 10 October 1871).
 * 3 July 1871: Blackfriars to Mansion House.
 * Also High Street Kensington to the West Brompton branch.
 * 1 February 1872: Earl's Court to Addison Road (renamed Kensington (Olympia) in 1946) on the West London Joint Railway.
 * 9 September 1874: Earl's Court to Hammersmith.
 * 1 June 1877: Hammersmith to Ravenscourt Park, where a connection was made with the London and South Western Railway (L&SWR), allowing District trains to run over L&SWR tracks to Richmond (The L&SWR branch to Richmond from Addison Road via stations at Shepherd's Bush and Hammersmith (Grove Road) had been opened in 1869).
 * 1 July 1879: Turnham Green - Ealing (now Ealing Broadway).
 * 1 March 1880: West Brompton to Putney Bridge & Fulham (now Putney Bridge).
 * 1 March 1883: Ealing Broadway to Windsor via a connection at Ealing Broadway to the Great Western Railway tracks. The service was withdrawn on 30 September 1885.
 * 1 May 1883: Mill Hill Park (now Acton Town) to Hounslow Town (closed shortly afterwards).
 * 21 July 1884: Osterley & Spring Grove (now Osterley) to Hounslow Barracks (now Hounslow West).
 * 6 October 1884: Mansion House to the MetR's Tower Hill. New tracks east of Tower Hill towards St. Mary's (now closed) enabled the District to reach Whitechapel and also connect to the East London Railway. District trains began to run to the London, Brighton and South Coast Railway's New Cross (now New Cross Gate) station. The trains used the Thames Tunnel to pass under the river.
 * 3 June 1889: Putney Bridge to Wimbledon, was opened by the L&SWR with the District having running rights.
 * 2 June 1902: Whitechapel to Bromley-by-Bow and, via a connection there, on to the London, Tilbury and Southend Railway and to Upminster.
 * 23 June 1903: Ealing Common to Park Royal & Twyford Abbey.
 * 28 June 1903: Park Royal & Twyford Abbey to South Harrow.
 * 13 June 1905: Acton Town to South Acton.
 * 1 March 1910: South Harrow to Rayners Lane where it met the MetR then continued, via MetR tracks, to Uxbridge.

This completed the Metropolitan District Railway system.

Electrification
Electrification had been considered by the MetR as early as the 1880s, but such a method of traction was still in its infancy, and agreement would need to be reached with the District because of the shared ownership of the Inner Circle. Experiments were later carried out on the Earl's Court-High Street Kensington section, and a jointly-owned train of six coaches began a passenger service in 1900. As a result of those tests a MetR/District committee in 1901 recommended overhead AC traction on the Ganz three-phase system. This was accepted by both parties but when an American led group, the Underground Electric Railways Company of London (UERL), took control of the District there was disagreement. The group was led by Charles Yerkes, whose experience in the United States led him to favour DC, with third-rail pickup similar to that in use on the City & South London Railway and Central London Railway. After arbritration by the Board of Trade the latter system was taken up and the railways began electrifying the routes, using multiple-unit stock.


 * In 1902 the District commenced building the Lots Road Power Station to supply power to their network, which opened in 1905.
 * 1 July 1905: Aldgate-Whitechapel, initially for the District service
 * 13–24 September 1905: gradual electrification of the Inner Circle
 * 5 November 1905: completion of the electrification of the District lines with the electrification of the Edgware Road-Hammersmith and the Addison Road (now Olympia) branch
 * 1 March 1910: Rayners Lane - South Harrow. This enabled the District to extend its services to Uxbridge