The socio-economic conditions that led to the growth of Kolkata, were urbanising a much larger territory. Right form the 16th century, a number of townships, based on trade and commerce, had sprung up along both banks of the Hooghly. None of these townships withered away as Kolkata gained supremacy, rather they got integrated with the core of the city. In 1951, census operations in West Bengal first recognised a continuous industrial area stretching from Bansberia to Uluberia on the west bank of the Hooghly, and from Kalyani to Budge Budge on the east bank. It was ultimately recognised as the Kolkata urban agglomeration, with the city as its core.