The Northern line is a deep-level tube line on the London Underground, coloured black on the Tube map.
It carries more passengers per year than any other Underground line.
Despite its name, the Northern line does not serve the northernmost stations on the Underground network although, ironically, it does serve the southernmost station and serves 16 of the Underground system’s 29 stations south of the River Thames: a proportion higher than any other line. Of the 50 stations on the Northern line, 36 are underground.
The London Northern line has a complicated history and the current complex arrangement of two northern branches, two central branches and the southern branch reflects its genesis as three separate railway companies that were brought together and combined in the 1920s and 1930s.
An extension in the 1920s used a route originally planned by a fourth company and abandoned plans to extend the line southwards in the 1920s and northwards in the 1930s would have incorporated parts of the routes of a two further companies. Each platform is 110 metres long