Ludhiana is a city and a municipal corporation in Ludhiana district in the Indian state of Punjab. It is the largest city in the state, with an estimated population of 1,613,878 in 2011. The population increases substantially during the crop harvesting season due to migration of laborers from states like Eastern Uttar Pradesh, Bihar, Orissa and Delhi. It has an area of about 310 km². The city stands on the Sutlej River's old bank, 13 km south of its present course. It is a major industrial center of northern India.