To finance electrification at the beginning of the 20th century, American financier Charles Yerkes took it over and made it part of his Underground Electric Railways Company of London (UERL) group.
For the 1864 parliamentary session, railway schemes were presented that met the recommendation in varying ways and a joint committee composed of members of both Houses of Parliament reviewed the options.
The Met's chairman and three other directors were on the board of the District, John Fowler was the engineer of both companies and the construction works for all of the extensions were let as a single contract.
During the night of 5 July 1870 the District secretly built the disputed Cromwell Curve connecting Brompton (Gloucester Road) and Kensington (High Street).
[13] East of Westminster, the next section ran in the newly constructed Victoria Embankment built by the Metropolitan Board of Works along the north bank of the River Thames.
Struggling under the burden of high construction costs, the District was unable to continue with the original scheme to reach Tower Hill and made a final extension of its line one station further east from Blackfriars to a previously unplanned City terminus at Mansion House.
[16] From this date, the two companies operated a joint inner circle service between Mansion House and Moorgate Street via South Kensington and Edgware Road that ran every ten minutes.
This curve allowed, from 1 February 1872, the London & North Western Railway (L&NWR) to run a half-hourly outer circle service from Broad Street to Mansion House via Willesden Junction, Addison Road and Earls Court.
From 1 October 1872, the GWR also ran a half-hourly middle circle service from the Met's Moorgate Street station to Mansion House via Paddington and Earl's Court.
It opened on 9 September 1874 with one intermediate station at North End (Fulham) (renamed West Kensington in 1877) and a terminus at Hammersmith, and was served by through trains to Mansion House.
[27] From 1 May 1878 to 30 September 1880, the Midland Railway operated a circular service from St Pancras to Earl's Court via Dudding Hill, Acton and the L&SWR to Hammersmith.
From 1 October 1884 the District and Metropolitan began local services from St Mary's via this curve onto the East London Railway to SER's New Cross station.
On the same day the District extended its services to Whitechapel and over the ELR to New Cross, calling at new joint stations at Aldgate East and St Mary's.
[41] Several schemes to cross the Thames at Putney Bridge to Guildford, Surbiton or Wimbledon had been proposed and received approval from Parliament, although the District had been unable to raise the necessary funding.
The LT&SR and District jointly took over the company the following year and the line opened on 2 June 1902 with new stations at Stepney Green, Mile End and Bow Road.
[45] At the start of the 20th century the District and Metropolitan railways faced increased competition in central London from new, electric, deep-level tube lines.
A jointly owned train of six coaches successfully ran an experimental passenger service on the Earl's Court to High Street Kensington section for six months in 1900.
Tenders were then requested and in 1901 a Metropolitan and District joint committee recommended the Ganz three-phase AC system with overhead wires.
On 15 July 1901, Yerkes established the Metropolitan District Electric Traction Company with himself as managing director[50] and raised £1 million to carry out the electrification, including construction of the generating station and supplying the new rolling stock.
After modification the Met returned and electric trains took over on 24 September, reducing the travel time around the circle from seventy to fifty minutes.
[83] Powers were renewed in 1926 for the quadruple track from Hammersmith to be extended to west of Acton Town, with the concept of the Piccadilly running non-stop on the inner pair.
[90] To protect the UERL group's income, its chairman Lord Ashfield lobbied the government for regulation of transport services in the London area.
Ashfield aimed for regulation that would give the UERL group protection from competition and allow it to take control of the LCC's tram system; Morrison preferred full public ownership.
[99] In 1905 the District bought ten bogie box cab locomotives that looked similar to their multiple units but were only 25 feet (7.6 m) long.
[100] The locomotives were used to haul L&NWR passenger trains on the electrified section of the Outer Circle route between Earl's Court and Mansion House.
[101] From 1910 the locomotives were used on London, Tilbury and Southend Railway (LT&SR) trains extended over the District line, west of Barking.
A third of the vehicles were made in England, the rest in Belgium and France and electrical equipment was installed on arrival at Ealing Common Works.
After the District Railway became part of London Underground, similar cars were ordered to allow the Metropolitan line be extended to Barking and replace some of the rapidly deteriorating original wooden trailers.
[118] The 1935–40 New Works Programme fitted electro-pneumatic brakes and air-operated doors to most of the District line stock[119] and allowed the remaining wooden cars to be scrapped.
[121] As of March 2015[update] a driving motor car built in 1923 is a static exhibit at London Transport Museum at Covent Garden.