West Bengal was formed after the reorganisation of States in 1956. It has a varied terrain, with mountains to the north and the plains and the Ganges Delta to the south. Agriculture provides livelihood to nearly 75 per cent of the population. The irrigated land area is 99,110 hectares and the major crops of the State are rice, wheat, pulses, jute, oilseeds and potatoes. West Bengal has several industries, namely leather, jute, silk and cotton, iron and steel and tea. The State has rich deposits of coal, dolomite and clay. The major ports are Calcutta and Haldia. West Bengal has hot tropical summers, mild winters, and the average annual rainfall is 228 cm.