Despite the commercial success, tea labourers continued to be exploited, working and living under poor conditions. Fearful of greater government interference, the tea growers formed the Indian Tea Association in 1888 to lobby to retain the status quo. The organisation was successful in this, but even after India's independence, conditions of the labourers have improved very little.
In the later part of the 18th century, religious tensions and atrocities by the nobles led to the Moamoria rebellion (1769–1805), resulting in tremendous casualties of lives and property. The rebellion was suppressed but the kingdom was severely weakened by the civil war. Political rivalry between Prime Minister Purnananda Burhagohain and Badan Chandra Borphukan, the Ahom Viceroy of Western Assam, led to an invitation to the Burmese by the latter, in turn leading to three successive Burmese invasions of Assam. The reigning monarch Chandrakanta Singha tried to check the Burmese invaders but he was defeated after fierce resistance. And Ahom occupied Assam was captured by the Burmese.
A reign of terror was unleashed by the Burmese on the Assamese people, who fled to neighbouring kingdoms and British-ruled Bengal. The Burmese reached the East India Company's borders, and the First Anglo-Burmese War ensued in 1824. The war ended under the Treaty of Yandabo in 1826, with the Company taking control of Western Assam and installing Purandar Singha as king of Upper Assam in 1833. The arrangement lasted till 1838 and thereafter the British gradually annexed the entire region. Thereafter the court language and medium of instruction in educational institutions of Assam was made Bengali, instead of Assamese. Starting from 1836 until 1873, this imposition of a foreign tongue created greater unemployment among the People of Assam and Assamese literature naturally suffered in its growth.
Initially, Assam was made a part of the Bengal Presidency, then in 1906 it was made a part of Eastern Bengal and Assam province, and in 1912 it was reconstituted into a chief commissioners' province. In 1913, a legislative council and, in 1937, the Assam Legislative Assembly, were formed in Shillong, the erstwhile capital of the region. The British tea planters imported labour from central India adding to the demographic canvas.
The Assam territory was first separated from Bengal in 1874 as the 'North-East Frontier' non-regulation province, also known as the Assam Chief-Commissionership. It was incorporated into the new province of Eastern Bengal and Assam in 1905 after the partition of Bengal (1905–1911) and re-established in 1912 as Assam Province.
After a few initially unsuccessful attempts to gain independence for Assam during the 1850s, anti-colonial Assamese joined and actively supported the Indian National Congress against the British from the early 20th century, with Gopinath Bordoloi emerging as the preeminent nationalist leader in the Assam Congress. Bordoloi's major political rival in this time was Sir Saidullah, who was representing the Muslim League, and had the backing of the influential Muslim cleric Maulana Bhasani.
The Assam Postage Circle was established by 1873 under the headship of the Deputy Post Master General.
At the turn of the 20th century, British India consisted of eight provinces that were administered either by a governor or a lieutenant-governor. Assam Province was one among the major eight provinces of British India. The table below shows the major original provinces during British India covering the Assam Province under the Administrative Office of the Chief Commissioner.