Elephant and Castle is one of five London tube stations named after a pub.
Nelson Square is a road in the SE1 postcode area
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One thing Elephant and Castle is not
named after is 'La Infanta de Castilla', seemingly referring to a series of Spanish princesses such as Eleanor of Castile and María, the daughter of Philip III of Spain. However, Eleanor of Castile was not an infanta - the term only appeared in English about 1600. María has a strong British connection because she was once controversially engaged to Charles I, but she had no connection with Castile. Infanta de Castilla
therefore seems to be a conflation of two Iberian royals separated by 300 years.
Regardless, the pub of that name gave its name to the station, and in turn the station to the nearby area - originally called Newington
Elephant & Castle tube station is on the Bank branch of the Northern Line between Kennington and Borough, and is the southern terminus of the Bakerloo Line.
The station was built in two stages. The Northern Line station opened on 18 December 1890 as part of the first deep-level tube, the City & South London Railway (C&SLR). The Baker Street & Waterloo Railway (BS&WR) station opened on 5 August 1906, five months after the rest of the line. Although belonging to separate companies, the platforms were connected below ground from 10 August 1906.
The first baby to be born on the underground was born at the station in 1924. Press reports claimed that she had been named Thelma Ursula Beatrice Eleanor (so that her initials would have read T.U.B.E.) but this story later proved false, and she was named Marie Cordery. Elephant and Castle seems to specialise in names which prove false!