The bank traces its ancestry to British India, through the Imperial Bank of India, until the founding, in 1806, of the Bank of Calcutta, making it the oldest commercial bank of the Indian subcontinent. Bank of Madras merged into the other two "presidency banks" in British India, Bank of Calcutta and Bank of Bombay, to form the Imperial Bank of India, which in turn became the State Bank of India in 1955. Bank of India in 1955, with the Central Bank of India taking a 60% stake, and renamed it the State Bank of India. In 2008, the government took over the holding of the Reserve Bank of India. State Bank of India is a banking giant and has a 20% market share in deposits and loans among Indian commercial banks.