London Bridge refers to several bridges that have spanned the River Thames between the City of London and Southwark. The current crossing opened to traffic in 1973 and is a box girder bridge constructed from concrete and steel. It replaced a 19th-century stone-arched bridge, which in turn superseded a 600-year-old medieval structure. This was preceded by a succession of timber bridges; the first was built by the Roman founders of London.
The current bridge still stands at the western end of the Pool of London but it is positioned 30 metres (98 ft) upstream from the original alignment. Until Putney Bridge opened in 1729, London Bridge was the only road-crossing of the Thames downstream of Kingston.
The modern bridge is owned and maintained by Bridge House Estates, an independent charity overseen by the City of London Corporation. The bridge carries the A3, which is maintained by the Greater London Authority. It was designed by architect Lord Holford and engineers Mott, Hay and Anderson. It was constructed by contractors John Mowlem and Co from 1967 to 1972, and opened by Queen Elizabeth II on 17 March 1973. It comprises three spans of pre-stressed-concrete box girders, a total of 928 feet (283 m) long. The cost of £4 million (£42.1 million as of 2013), was met entirely by the Bridge House Estates charity. The current bridge was built in the same location as Rennie’s bridge.
In 1984, the British warship HMS Jupiter collided with London Bridge, causing significant damage to both ship and bridge. The current London Bridge is often shown in films, news and documentaries showing the throng of commuters journeying to work into The City from London Bridge Station (south to north).
See more at http://www.history.co.uk/study-topics/history-of-london/london-bridge