Digboi is known as the Oil City of Assam where the first oil well in Asia was drilled. The first refinery was started here as early as 1901. Digboi has the oldest oil well in operation. With a significant number of British professionals working for Assam Oil Company until the decade following independence of India, Digboi had a well-developed infrastructure and a number of bungalows unique to the town.

Today, though the crude production is not high, Digboi has the distinction of being India’s oldest continuously producing oilfield. Digboi refinery, now a division of Indian Oil Corporation, had a capacity of about 0.65 MMTPA as of 2003. The Digboi refinery is the world’s oldest oil refinery still in operation.

Source: http://en.wikipedia.org/wiki/Digboi