Baker Street station was opened by the MR on 10 January 1863 (these platforms are now served by the Circle and Hammersmith & City lines). The Baker Street & Waterloo Railway (BS&WR, now the Bakerloo line) opened on 10 March 1906; Baker Street was the temporary northern terminus of the line until it was extended to Marylebone station on 27 March 1907. The original station building stood on Baker Street and served the tube platforms with lifts, but these were supplemented with escalators in 1914, linking the Metropolitan line and the Bakerloo line platforms by a new concourse excavated under the Metropolitan line. On 20 November 1939, following the construction of an additional southbound platform and connecting tube tunnels between Baker Street and Finchley Road stations, the Bakerloo line took over the Metropolitan line's stopping services between Finchley Road and Wembley Park and its Stanmore branch. The current Bakerloo ticket hall and escalators to the lower concourse were provided in conjunction with the new service.
The station layout is rather complex. The sub-surface station is connected to the open-air Metropolitan line station. This is a terminus for some Metropolitan line trains, but there is also a connecting curve that joins to the Circle line just beyond the platforms that allows Metropolitan line trains to run to Aldgate in the City of London. Below this is a deep-level tube station for the Bakerloo and Jubilee lines. These are arranged in a cross-platform interchange layout and there are connections between the two lines just to the north of the station. Access to the Bakerloo and Jubilee lines is only via escalators. With ten platforms overall, Baker Street has the most London Underground platforms of any station on the network. The station has a bridge, cash machines, Euro cash machines, payphones, toilets, wi-fi and escalators.
Connections: Metropolitan, Circle, Hammersmith + City, Jubilee Lines. London Bus routes 2, 13, 18, 27, 30, 74, 82, 113, 139, 189, 205, 274 and 453, and night routes N13, N18, N74, N113 and N205 serve the station. In addition, bus routes 27, 139, 189 and 453 have a 24-hour service.