signing of the Sugauli Treaty in 1815. According to the treaty, Nepal had to cede all those territories which the Gorkhas had annexed from the Chogyal of Sikkim to the British East India Company (i.e., the area between Mechi River and Teesta River). In 1817, through the Treaty of Titalia, the British East India Company reinstated the Chogyal of Sikkim, restored all the tracts of land between the Mechi and the Teesta rivers to the Chogyal of Sikkim and guaranteed his sovereignty. In 1835, the hill of Darjeeling, including an enclave of , was given to the British East India Company by Sikkim. In November 1864, the Treaty of Sinchula was executed in which the Bhutan Dooars with the passes leading into the hills and Kalimpong were ceded to the British by Bhutan. The Darjeeling district can be said to have assumed its present shape and size in 1866 with an area of 1234 sq. miles. Before 1861 and from 1870 to 1874, Darjeeling District was a "Non-Regulated Area" (where acts and regulations of the British Raj did not automatically apply in the district in line with rest of the country, unless specifically extended). From 1862 to 1870, it was considered a "Regulated Area". The phrase "Non-Regulated Area" was changed to "Scheduled District" in 1874 and again to "Backward Tracts" in 1919. The status was known as "Partially Excluded Area" from 1935 until the independence of India. On 14 February 2017, Kalimpong district was carved out of Darjeeling district. Gorkhaland Movement During the 1980s, the Gorkha National Liberation Front led an intensive and often violent campaign for the creation of a separate Gorkhaland state within India, across the Nepali-speaking areas in northern West Bengal. The movement reached its peak around 1986–1988 but ended with the establishment of the Darjeeling Gorkha Hill Council in 1988. The hill areas of Darjeeling enjoyed some measure of autonomy under the Darjeeling Gorkha Hill Council. However, the demand for full statehood within India has emerged once again, with the Gorkha Janmukti Morcha as its chief proponent. The Gorkhaland Territorial Administration replaced the DGHC in August 2012 after the GJM signed an agreement with the government. Geography The Darjeeling hill area is formed of comparatively recent rock structure that has a direct bearing on landslides. Heavy monsoon precipitation contributes to the landslides. Soils of Darjeeling hill areas are extremely varied, depending on elevation, degree of slope,