The Hammersmith and City line opened as the Metropolitan Hammersmith Railway and was a subsidiary of the Great West Railway and Metropolitan Railway.

The Metropolitan Hammersmith Railway

Following the success of the Metropolitan Railway, there was a surge of railways and extensions proposed. An extension westwards to the Metropolitan Railway was strongly supported and the route to Hammersmith had particular appeal because it was supported by the Great Western Railway (GWR), operating from Paddington Station. This extension would entail constructing the new railway a mile from the railway terminus at Paddington into the suburbs at Shepards Bush and Hammersmith; the railway would be constructed over open fields on viaducts.

The extension to the railway opened on 13 June 1864, with the Great Western Railway (GWR) operating services between Farringdon and Hammersmith. A link was opened shortly after the opening of the extension to allow services to run to Addison Road (Kensington Olympia today) via the West London Railway though a link at Latimer Road.

This service was amended in 1864, with the Great Western Railway (GWR) taking services running to Addison Road and the Metropolitan Railway running services to Hammersmith. The railway became jointly owned in 1867; this prompted the introduction of two additional tracks to be laid between Wetbourne Park and Paddington for use by the railway which was completed in 1871. The flat crossing at Westbourne Park was replaced with a dive under in 1878.

The railway operated two gauges, the standard 1.43m (4ft 8½in) for Metropolitan Railway services and the board guage 2.13m (7ft 0 ¼in) for Great Western Railway (GWR).

The service was extended to Richmond over the London and South Western Railway (L&SWR) via Hammersmith (Grove Road) station in 1877, with the eastern service also being extended on 18 November 1876 to Aldgate. However, the Metropolitan Railway wanted to extend the railway further, publishing a plan to extend the railway over the South Eastern Railways East London Railway to Whitechapel providing a connection with the Dictrict Railway, which was being extended eastwards beyond Mansion House. The service was extended to New Cross from Hammersmith in October 1884 with the extension making use of the East London Railway.

The Whitechapel and Bow Railway was completed in 1902, providing a vital connection at the above ground station at Bow and allowed the District Railway to extend its services to Whitechappel. The District Railway services where extended to East Ham.

The Hammersmith and City Railway was reduced during electrification, with services to Richmond being withdrawn in 1906 and the traffic being diverted to Hammersmith or Addison Road and running though to Whitechappel. The services to New Cross and New Cross Gate where officially withdrawn in 1914 when the East London Railway was electrified.

The Metropolitan Railway branch

The Metropolitan Hammersmith Railway was amalgamated into the London Transport Passenger Board on 1 July 1933 along with the other underground railways, London tramway and bus operators.

To relive congestion on the District Railway east of Whitechapel in 1936, some Hammersmith services continued to Barking. This was changed in November 1939, with shorter Hammersmith services terminating at Whitechapel and longer 8-car Uxbridge services running to Barking, with all services from Hammersmith to New Cross or New Cross Gate being withdrawn. Barking became the final termini for all Hammersmith services in 1941.

New rolling stock was introduced to the railway in 1937, this replaced the original wooden-bodied rolling stock from the 1906, these boasted doors which where remotely operated by guards. The original intention was to operate four and six car formations, however this proved problematic and the stock was introduced in a six-car formation.

The railway remained mostly in operation during the war, there was one change, in 1940 the service to Kensington Olympia was suspended because of bomb damage to the curve at Latimer Road. This service was quickly restored after the war.

During the period between 1959 and 1960, the Circle and Hammersmith and City stock where converted to the same formation and both lines principle depot was moved to Hammersmith.

New rolling stock was introduced from 1970, these boasted a public address system and where left unpainted when they entered service. The new rolling stock also brought the idea of introducing One Person Operation in 1972, howerver due to a dispute with the trade unions this didn't happen until 1984.

The Hammermith and City line today

The Hammersmith and City line operated as a part of the Metropolitan Railway until 30 July 1990, when the route from Hammersmith to Barking became the The Hammersmith and City line. The Metropolitan line remains the route from Aldgate to Bakers Street and northwards to Uxbridge, Watford and Amersham.

The reconstruction of Whitechapel station for Crossrail has seen the reversing platform removed preventing services from terminating and Hammersmith and City line services where extended in 2009 to terminate at Plaistow or Barking.

The Hammersmith and City line spans 14.5km (9 miles) serving 28 stations and requires 17 trains to operate the morning peak.