<P> In 1973, anti-royalty riots in front of the palace led to a formal request for protection from India . India worried that an unstable Sikkim would invite China to act on its claims that Sikkim was part of Tibet, and therefore part of China . The Indian government appointed a Chief administrator, Mr. B.S. Das, who effectively wrested control of the country away from the Chogyal . </P> <P> Frosty relations between the Chogyal and the elected Kazi (Prime Minister) Lhendup Dorji resulted in an attempt to block the meeting of the legislature . The Kazi was elected by the Council of Ministers which was unanimous in its opposition to the retention of the Monarchy . </P> <P> Prime Minister Dorji appealed to the Indian Parliament for representation and change of status to statehood . On 14 April 1975, a referendum was held, in which Sikkim voted to merge with the union of India . Sikkim became the 22nd Indian State on 26 April 1975 . On 16 May 1975, Sikkim officially became a state of the Indian Union and Lhendup Dorji became head of State (chief minister). </P> <P> The position of Chogyal was thus abolished, ending the monarchy . In 1982, Palden Thondup died of cancer in the United States . </P>

When did sikkim become full fledged state of india