Of these, Sikkim became an Indian protectorate in 1947 and a full state in 1975. The states border Nepal, Bhutan, China, Myanmar and Bangladesh. However they share only a 21 km common border with the rest of India via the Siliguri Corridor (Chicken's Neck).
(For detailed history please see the articles on the individual states) The North-East has been added to political India only in recent times, though India itself was rarely unified for most of its history. Assam (which included at the time of Indian independence, Nagaland, Mizoram and Meghalaya) was rarely part of political India for most of its history; Manipur and Tripura were princely states also rarely a part of political India; Arunachal Pradesh was beyond the outer line of British India at the beginning of the 20th century; and Sikkim too was not part of political India. These areas were incorporated into mainstream India during the British Raj when British colonial authorities annexed traditionally separate border countries into Indian territory to form a buffer between their colony and external powers (ie: Assam, Manipur and Tripura in the Northeast, and Balochistan and the North West Frontier Province in the northwest). After independence in 1947, extension of the Indian state and political apparatus has been a challenge.
North-East India has a predominantly humid sub-tropical climate with hot, humid summers, severe monsoons and mild winters. Along with the west coast of India, this region has some of the Indian sub-continent's last remaining rain forests. The states of Arunachal Pradesh and Sikkim have a montane climate with cold, snowy winters and mild summers.
The northeastern states, having a comparitively small electorate (3.8% of India's total population) are alloted just 25 out of a total of 543 seats in the Lok Sabha (4.6% of the total number of seats).
The northeastern states are home to many ethnic groups, that are engaged in self-preservation. In recent times, some of these struggles have turned violent, leading to proliferation of armed insurgent groups, like the ULFA, NLFT, NDFB and NSCN. Soon after the Sino-Indian War of 1962 and especially after the rise of insurgency in the region, security influence on policies has increased.
The region is known for its unique culture, handicrafts, martial arts, and scenic beauty. Problems include insurgency, unemployment, drug addiction, and lack of infrastructure. Since the beginning of the economic liberalization in the 1990s, studies have shown that this region is lagging behind the others in terms of development.