Around 4th century, Assam and its surroundings were known as Kamprup, and was ruled by Varmans, Bhaskar Varman being the most prominent king. Later they were under the rule of Mlechchha dynasty and Kamprup-Palas. All the three dynasties claimed their lineage from Narakasur. The kingdom disintegrated after the Kamrup-Palas.
Three later dynasties came up in the Medieval period, Ahoms, Sutias and the Koch. Ahoms, a Tai group originally from Yunan province in China, ruled upper Assam for nearly 600 years (1228-1826 AD). The Sutiya rulers (1187 -1673 AD) reigned on the north banks of Brahmaputra, their kingdom stretching from Vishwanath in the west to Parshuram Kund in the east in Upper Assam and in the state of Arunachal Pradesh. The Koch, of Tibeto-Burmese origin became sovereigns in 1510 AD. The Ahoms were at their zenith during the reign of Sukhrungpha or Sworgodeu Rudra Simha (c. 1696–1714 AD). The Ahom kingdom was run over by the Burmese in 1820s, who took control of the entire Brahmaputra valley.
British, in their campaign against the Burmese, annexed first lower, and then upper Assam. This led to the treaty of Yandaboo. Later, the remaining kingdoms, including Kacharis and Khasis were also brought under the British empire. In 1874, Assam was declared a separate state, with Shillong as its capital.
With the discovery of Camellia sinensis (tea plant), led to widespread tea plantations in Eastern Assam, where soil and climate were most suitable.
In 1905, Assam was amalgamated with East Bengal. 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.
After a few initial 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.
In 1979, Assam flared into Assam Agitation (or Assam Movement) a popular movement against illegal immigration. The movement, led AASU and AAGSP, two local parties, led an agitation to compel the government to identify and expel illegal immigrants and prevent new immigration. The agitations were largely non-violent, but there were incidents of acute violence, like the Nellie massacre. It ended in 1985 following the Assam Accord that was signed by the agitation leaders and the Government of India. The leaders of the agitation formed a political party, Asom Gana Parishad, which came to power in the state of Assam in the Assembly elections of 1985.