Metropolitan District Railway

The Metropolitan District Railway (MDR) was formed in 1864 in order to raise capital to complete the 'Inner Circle' railway being constructed by the Metropolitan Railway, who constructed the line between Mansion House and South Kensington via Kings Cross. The MDR completed the section of line between South Kensington and Mansion House via Blackfriars, finishing by 1871. The expectation was that the two companies would merge once work was completed. However, they instead had a falling out over finances (and a personality clash of the two Chairmen) and began to run separate services using the same lines. Some agreement was eventually reached so that the final section of line, between Mansion House and Aldgate, was completed in 1884, thus forming the modern day Circle Line.

In an attempt to improve their finances the MDR embarked on a series of line expansions, to Hammersmith in 1874, Richmond in 1877, Ealing Broadway in 1879, Putney Bridge in 1880, Hounslow in 1883, and Wimbledon in 1889. The Whitechapel to Upminster line extension was opened in 1902. The line was electrified in 1905, following the construction of a power station at Lots Road. The majority of the line cosntructed by the MDR forms the modern London Underground District Line, although some sections of line (Ealing to Uxbridge) are now on the Piccadilly Line. The MDR was purchased by Underground Electric Railways Company of London Limited and subsequently became part of the London Passenger Transport Board in 1933.