Editing London Underground (section)

===Underground Electric Railways Company era===
[[File:Baker Street Waterloo Railway platform March 1906 (cropped).jpg|right|thumb|Passengers wait to board a tube train in 1906.|alt=Sketch showing about a dozen people standing on an underground railway platform with a train standing at the platform. Several more people are visible inside the train, which has the words "Baker St" visible on its side.]]
Yerkes soon had control of the District Railway and established the [[Underground Electric Railways Company of London]] (UERL) in 1902 to finance and operate three tube lines, the [[Baker Street and Waterloo Railway]] (Bakerloo), the [[Charing Cross, Euston and Hampstead Railway]] (Hampstead) and the [[Great Northern, Piccadilly and Brompton Railway]], (Piccadilly), which all opened between 1906 and 1907.{{sfnp|Day|Reed|2010|pp=69–72, 78}}{{sfnp|Green|1987|p=30}} When the "Bakerloo" was so named in July 1906, ''[[The Railway Magazine]]'' called it an undignified "gutter title".{{sfnp|Green|1987|p=30}} By 1907 the District and Metropolitan Railways had electrified the underground sections of their lines.{{sfnp|Green|1987|pp=24–28}}

In January 1913, the UERL acquired the [[Central London Railway]] and the [[City & South London Railway]], as well as many of London's bus and tram operators.{{sfn|Wolmar|2004|p=204}} Only the [[Metropolitan Railway]], along with its subsidiaries the [[Great Northern & City Railway]] and the [[East London Railway]], and the [[Waterloo & City Railway]], by then owned by the main line [[London and South Western Railway]], remained outside the Underground Group's control.{{sfn|Wolmar|2004|p=205}}

A joint marketing agreement between most of the companies in the early years of the 20th century included maps, joint publicity, through ticketing and U<small>NDERGROUN</small>D signs, incorporating the first bullseye symbol,<ref name=":4">Ackroyd, P. (2012). London Under. London: Vintage Books. {{ISBN|978-0-099-28737-7}}</ref> outside stations in Central London.{{sfnp|Horne|2003|p=51}} At the time, the term Underground was selected from three other proposed names; 'Tube' and 'Electric' were both officially rejected.<ref name=":4" /> Ironically, the term Tube was later adopted alongside the Underground. The Bakerloo line was extended north to Queen's Park to join a new electric line from Euston to [[Watford]], but the [[First World War]] delayed construction and trains reached {{rws|Watford Junction}} in 1917. During [[Airstrike|air raids]] in 1915 people used the tube stations as shelters.{{sfnp|Green|1987|p=35}} An extension of the Central line west to [[Ealing]] was also delayed by the war and was completed in 1920.{{sfnp|Green|1987|p=33}} After the war, government-backed financial guarantees were used to expand the network and the tunnels of the City and South London and Hampstead railways were linked at Euston and Kennington;{{sfnp|Day|Reed|2010|p=94}} the combined service was not named the Northern line until later.{{sfnp|Day|Reed|2010|p=122}} The Metropolitan promoted housing estates near the railway with the "[[Metro-land]]" brand and nine housing estates were built near stations on the line. Electrification was extended north from Harrow to [[Rickmansworth]], and branches opened from Rickmansworth to Watford in 1925 and from Wembley Park to Stanmore in 1932.{{sfnp|Day|Reed|2010|pp=84–88}}{{sfnp|Jackson|1986|pp=134, 137}} The [[Piccadilly line]] was extended north to [[Cockfosters]] and took over District line branches to Harrow (later Uxbridge) and Hounslow.{{sfnp|Day|Reed|2010|p=98–103, 111}}