The State Bank of India traces its ancestry to British India, when the Bank of Calcutta was established on 2 June 1806. The Bank of Bengal was one of three Presidency banks, the other two being the Bank of Bombay (1840) and the Bank of Madras (1843). The Presidency banks amalgamated on 27 January 1921 as the Imperial Bank of India. On 1 July 1955, the Imperial Bank of India became the State Bank of India.