The district of Katihar became a full-fledged district after it split from the district of Purnia in 1973. Earlier, it was a part of Bengal. However, when the partition of India divided the region of Bengal into Bihar, Bengal and Orissa, the district came under the jurisdiction of Bihar. Because of this historicity, the district is culturally very close to the culture of Bengal and the festivals in Bengal are widely celebrated in the district. It is also a historically a key Railway district, with the starting point of the North East Frontier Railways being located in Katihar.

Katihar has an area of approximately 3,000 square kilometres and is situated mostly in the plains of the North Eastern part of the State of Bihar. It is surrounded by Purnia (Bihar) in the north, Bhagalpur (Bihar) on the west, Sahebganj (Jharkhand) in the sound and Malda (West Bengal) and Uttar Dinajpur (West Bengal) in the east. Rice, jute, maize and rice appears to be the major crops in the area and it is also a trading district that connects the North Eastern part of the country to the rest of the country.

It has a population of about 3,00,000 people and has a density of about 1,004 inhabitants per square kilometre. It has a sex ratio of 916 women for every 1000 men and has a very low literacy rate of 53.56%. Apart from Hindi, Surjapuri and Bengali are also extensively used in the district.