[7] The party split in 2005, with former Chief Minister Prafulla Kumar Mahanta forming the Asom Gana Parishad (Progressive), but regrouped on 14 October 2008 in Golaghat.

In 1979, AASU led what started as a nonviolent campaign to highlight illegal immigration into the state, but later descended into violence.

The AASU, joined by the AGSP demanded detection and disenfranchisement of all illegal migrants in the state, and deportation of all immigrants entering the country from 1951 on under the laws of the land.

One of the most serious outcomes of the ethnic violence that ensued came to be known as the Nellie massacre when anti-immigrant groups attacked and killed at least 2,000 Muslim, Bengali immigrants.

The State Assembly was then dissolved and the Congress government headed by Hiteswar Saikia, who came to power in February 1983, was dismissed.

The AGP contested the State Assembly elections held in December 1985 and swept the polls by winning 67 of the 126 seatsin addition to capturing seven of the 14 Lok Sabha (Parliament) seats thus forming the Government of Assam.

Party leader Prafulla Kumar Mahanta served as the Chief Minister of Assam for two terms, first from 1985 to 1990 and again from 1996 to 2001.

AGP Member of Parliament Dinesh Goswami was the Union Minister of Law and Justice in the V. P. Singh Ministry.

The party also took part in the United Front governments headed by H. D. Deve Gowda and Inder Kumar Gujral.

On 8 February 2011, Sonowal joined Bharatiya Janata Party in the presence of the then BJP National President Nitin Gadkari and senior leaders like Varun Gandhi, Vijay Goel, Bijoya Chakravarty and state BJP president Ranjit Dutta.

[14] In November 2016, Atul Bora was elected for President of Asom Gana Parishad second time amending party's constitution ‘one man one post’ as he is also minister of Agriculture, Horticulture and Food Processing, Animal Husbandry and Veterinary in Sarbananda Sonowal Ministry.