The History of Sikkim begins with the invasion of Buddhism and the Founding of Namgyal Dynasty. In the middle of 15th century Khey Bhumsa came to Sikkim from Tibet in search of the Lepcha Chieftain Thekung Thek to seek his blessing (who was also a religious leader). Khey Bhumsa was blessed with three son, during the blessing Thekung Thek prophesied that his successors would be the ruler of Sikkim. Out of being grateful Khey Bhumsa visited Sikkim numerous times and as the times pass by the relation of friend ship changed into a treaty of Brotherhood. This treaty not only brought the two great people closer but also brought a two community of Lepcha and Bhutia into a ties of Brotherhood.
Khey Bhumsa third son Mipon Rab became his successor and assumed the chief ship of Bhutias. He had four son among which Guru Tashi succeeded him and shifted to Gangtok. On the other Hand after the death of Lepcha Chieftain The Lepcha broke into minor clans. They gradually turned to Guru Tashi for protection ans leadership. Sambre (One of the Lepcha Member) was appointed as Chief Advisor and lieutenant by Guru Tashi. Guru Tashi became the first ruler of Sikkim and was crowned as such. and so on his heridetary moved on untill in the year 1642 when the three lamas from three different direction crowned Phuntsok Namgyal (great grand son of Guru Tashi) as the official King of Sikkim. He was given the title of Namgyal and the title of Chogyal or the religious King of Sikkim.
After Phuntsok Namgyal his son became the next King Chador Namgyal and so the Namgyal hereditary went through till the last King Palden Thondup Namgyal. The Namgyal Dynasty ruled Sikkim for about 332 years.
During  the 18th and 19th century the people from Nepal and Bhutan entered Sikkim with the invasion of British in search of trade route to Tibet. This Invasion brought upon a very big change in the ethnic balance in Sikkim. By the first 19th century Sikkim had became of protectorate of British and later India was inherited when British left. The 50's and 60's saw a series of Polotical development in Sikkim. Democratic aspiration in the people was awakened which later on resulted in the over throw of the monarchy and culminated. On 4th Sept. 1974 Kazi Lendup Dorjee was elected the first chief Minister of Sikkim. B. B. Lall was the first governor of Sikkim. and on 16th May 1975 Sikkim became the 22nd State of India.