The London Stock Exchange (LSE) is the primary stock exchange in the United Kingdom and its largest. Originating more than 300 years ago, the regional exchanges were merged in 1973 to form the Stock Exchange of Great Britain and Ireland, later renamed the London Stock Exchange (LSE). The Financial Times Stock Exchange (FTSE) 100 Share Index, or "Footsie", is the dominant index, containing 100 of the top blue-chip stocks on the LSE.