An underground station to serve Euston station was first proposed by the Hampstead, St Pancras & Charing Cross Railway in 1891. The company planned a route to run from Heath Street in Hampstead to Strand in Charing Cross with a branch diverging from the main route to run under Drummond Street to serve Euston, St Pancras and King's Cross stations. In 1900, a proposal was presented to parliament by the Islington and Euston Railway (I&ER) for an extension of the City and South London Railway (C&SLR) from Angel to Euston. With funding obtained, tunnelling for the CCE&HR was carried out between September 1903 and December 1905, after which the station buildings and fitting-out of the tunnels commenced. The C&SLR's Euston extension was constructed at the same time from the newly opened Angel station and opened on 12 May 1907, with the station building designed by Sidney Smith located on the east side of Eversholt Street.
The CCE&HR opened on 22 June 1907, its building, designed by Leslie Green, is located at the corner of Drummond Street and Melton Street. Although built and initially operated as two separate stations by the two companies, the C&SLR and the CCE&HR platforms were sufficiently close together that a deep level interchange was constructed between the passages of the two stations with a small ticket office for passengers changing between the lines. Another passage led to lifts that surfaced within the mainline station itself. With the entrance within the mainline station able to serve both sets of platforms satisfactorily, the separate station buildings were unneeded and they both closed on 30 September 1914.
There are four Northern line platforms as the station serves both the Bank branch (Platform 1 - N, 2 - S) and the Charing Cross branch (platform 3 - N, 6 - S). Future plans are to connect it to Euston Square (the Hammersmith and City lines) and a Crossrail link. The southbound Bank platform is extra wide as it covers the earlier Northbound tracks.
Connections: National Rail. Victoria Line and Bank and Charing Cross Northern Lines. London Bus routes 18, 59, 68, 91, 168, 253 and 476 and night routes N5, N20, N91 and N253 serve Euston bus station outside the mainline station.