In the earliest times Assam was known as Kamrupa a state that had its capital at Pragjyotisapura (modern Guwahati). Ancient Kamarupa included roughly the Brahmaputra valley, Bhutan, the Rangpur region (now in Bangladesh), and Koch Bihar, in West Bengal. King Narakasura and his son Bhagadatta were famous rulers of Kamarupa in the Mahabharata period (at least as early as 1000 BC).

Ahom, a tribe from Chinese province of Yunnan who migrated into Indochina and northern Myanmar in the first centuries AD, established a strong kingdom in Assam in the 13th century. The Ahom rule reached its peak during the reign of King Rudra Singh (1696–1714). 1816 Myanmar invaded Assam and ruled an oppressive rule. The kingdom is finally taken over by the British rule in 1826. The population of Assam consists of Indo-Iranian and Asian peoples.

Little is known of Meghalaya and Nagaland prior to the British period apart from the Medieval-chronicles of the neighbouring Ahoms and Kacharis of Assam.

The tribal hill people of Meghalaya trace their origin to pre-Aryan times in India. In the early 19th century, the British desire to build a road through the region in order to link Bengal and Assam led to a treaty (1827) with the ruler (syiem) of the Khasi principality of Nonkhlaw.

The Nagas, classified among the Indo-Asiatic peoples, form more than 20 tribes, as well as numerous sub-tribes, each having a specific geographic distribution. Though sharing many cultural traits, these tribes have maintained a high degree of isolation and lack cohesion as a single people. The Konyaks are the largest tribe, followed by the Aos, Tangkhuls, Semas, and Angamis. Two-thirds of Nagas has converted to Christianity, and most others are Hindu or Muslim. The 1816 Myanmar invasion of Assam led to oppressive Myanmar rule in Nagaland until the establishment of British rule over Assam in 1826. The British administration by 1892 encompassed the whole of Naga territory.

Similarly, little is known of Mizoram's early history. The various ethnic groups of Mizoram are known collectively as the Mizo (Lushai) who speak a variety of Tibeto-Burman dialects. Between 1750 and 1850 these tribes migrated from the nearby Chin Hills and subjugated the indigenous population; these similar tribes were assimilated into their own society. The Mizo developed an autocratic political system based on some 300 hereditary chieftanships.

Most of the population of Arunachal Pradesh is of Asiatic origin and shows physical affinities with the peoples of Tibet and the Myanmar hill region. The population consists of many ethnic groups who speak dialects of the Tibeto-Burman linguistic family.There are dozens of tribes and sub-tribes, each with a specific geographic distribution. In western Arunachal Pradesh the main tribes are the Nissi (Nishi or Dafla), Sulung, Sherdukpen, Aka, Monpa, Apa Tani, and Hill Miri.

Manipur’s earliest recorded history goes back to AD 900. The beginning of Manipur's more recent history dates from 1762, when the raja Jai Singh concluded a treaty with the British to repel an invasion from Myanmar. British assisted Manipur in repelling another Burmese invasion in 1824. The British administered the area in the 1890s, but in 1907 a local government took over. In 1947 Manipur acceded to the Indian union; it was ruled as a union territory until it became a state in 1972. About two-thirds of the people are the Meithei, who occupy the Manipur valley and are largely Hindus. Indigenous hill tribes, such as the Nagas in the north and the Kukis in the south make up the rest of the population divided into numerous clans and sections.

Tripura was an independent Hindu kingdom for more than 1,000 years before it became part of the Mughal Empire in the 17th century. After 1808 it was under the influence of the British government. Tripura became a union territory in 1956 and acquired full status as a state in 1972.

By 1826 the British had made most of the northeast India part of British India. In the division of India (1947) at the time of independence, Assam lost some territory to Pakistan (now Bangadesh). Beginning in the 1960s, four new states viz., Nagaland, Meghalaya, Mizoram, and Arunachal Pradesh were created from land within Assam. Mizoram, initially a union territory, was promoted to full statehood in 1987 following decades of discontent and rebellion.