Following months of political turmoil and a referendum in which over 97% of voters backed merging with India, Sikkim's monarchy under Chogyal Palden Thondup Namgyal was dissolved. The annexation extended India's northeastern frontier and remains a point of historical friction with China, which only formally recognized Sikkim as Indian territory in 2003.
Sikkim had existed for centuries as a Himalayan buffer kingdom between India, Nepal, Bhutan, and Tibet, ruled by a Buddhist monarch known as the Chogyal. Under a 1950 treaty, India controlled Sikkim's defense and foreign affairs while the kingdom retained internal autonomy, an arrangement that grew increasingly strained as Sikkimese politics fractured along ethnic and class lines.
By the early 1970s, the Nepali-majority population, long resentful of the political dominance of the ruling Bhutia-Lepcha elite, agitated for democratic reforms. India, wary of Chinese influence in the Himalayas after the 1962 border war, backed the pro-democracy movement. Indian troops effectively took control of Sikkim's capital Gangtok in 1973, and the monarchy's authority collapsed.
A referendum on April 14, 1975, produced a lopsided result favoring abolition of the monarchy and full merger with India. On May 16, 1975, Sikkim officially became India's 22nd state (the process culminating from actions initiated mid-month), and the last Chogyal, Palden Thondup Namgyal, was reduced to a figurehead before his death in 1982. China did not recognize the annexation for decades, treating it as a lingering territorial dispute.
Key people: Palden Thondup Namgyal, Indira Gandhi