London is the capital and most populous city of England and the United Kingdom. Standing on the River Thames, London has been a major settlement for two millennia, its history going back to its founding by the Romans, who named it Londinium. London's ancient core, the City of London, largely retains its 1.12-square-mile (2.9 km2) medieval boundaries and in 2011 had a resident population of 7,375, making it the smallest city in England. Since at least the 19th century, the term London has also referred to the metropolis developed around this core. The bulk of this conurbation forms Greater London, a region of England governed by the Mayor of London and the London Assembly. The conurbation also covers two English counties, the City of London and the county of Greater London, though historically it was split between the City, Middlesex, Essex, Surrey, Kent and Hertfordshire.