On 29th September 1989, the creation of the Bongaigaon District was declared by the Government of Assam with its headquarter at Bongaigaon. The major portion of the areas of erstwhile Bijni and Sidli estates along with tracts of Eastern Duars was curved out of Goalpara and Kokrajhar District in October 1989 in order to create the newest district of Assam, i.e. Bongaigaon.
The district has three subdivisions: Bongaigaon, Bijni and North Salmara. In 2004, parts of the Bongaigaon district (mainly areas under Bijni subdivision) were given over to form the Chirang district, under the Bodoland Territorial Council (BTC), with its district headquarters at Kajalgaon.
There are four Assam Legislative Assembly constituencies in this district: Bongaigaon, Bijni, Abhayapuri North, and Abhayapuri South. The latter is designated for scheduled castes. Bijni is in the Kokrajhar Lok Sabha constituency, whilst the other three are in the Barpeta Lok Sabha constituency.
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