Kishanganj district occupies an area of 1,884 square kilometres (727 sq mi), comparatively equivalent to Maui in the United States. Kishanganj district is surrounded by Araria district in the west, Purnia district in the south-west, Uttar Dinajpur district ofWest Bengal on the east, and Darjeeling district of West Bengal and Nepal on the north. A narrow strip of West Bengal, about 20 km wide separates it from Bangladesh.
According to the 2011 census Kishanganj district has a population of 1,690,948, roughly equal to the nation of Guinea-Bissau or the US state of Idaho. This gives it a ranking of 293rd in India (out of a total of 640). The district has a population density of 898 inhabitants per square kilometre (2,330 /sq mi) . Its population growth rate over the decade 2001-2011 was 30.44%.Kishanganj has a sex ratio of 946 females for every 1,000 males, and a literacy rate of 57.04%.
During the period of Khagada Nawab, Mohammed Fakiruddin, one hindu saint arrived , he was tired and wanted to rest at this place, but when he heard that this place name is Alamganj ,the river name is Ramzan and the Jamindar name is Fakiruddin , he refused to enter at Alamganj. After that the Nawab decided and announced some portion from Kishanganj Gudri to Ramzan pool gandhi ghat as Krishna-Kunj . As time passed by the name gets converted to present KISHANGANJ.
During Mughal period Kishanganj district was the part of Nepal and was known as Nepalgarh. Mughal Emperor Shah Alam appointed Mohammed Raza at Surajapur for administration. Md. Raza captured the fort of Nepalgarh and name gets converted to Alamganj and administration gets shifted to Khagara. The Historical "KHAGRA MELA" is held every year at Khagara, Kishanganj.