The history of Darjeeling is intertwined with that of Bengal, Sikkim and Nepal. Until the early 19th century, the hilly area around Darjeeling was historically controlled by the kingdom of Sikkim, while the plains around Siliguri were intermittently occupied by the kingdom of Nepal, with settlement consisting of a few Villages of Lepcha & Kirati people. It is also known that Nepal once expanded its kingdom up to the Teesta River. In 1828, a delegation of British East India Company officials on its way to Nepal-Sikkim border stayed in Darjeeling and decided that the region was a suitable site for a sanatorium for British soldiers. The company negotiated a lease of the area west of the Mahananda River from the Chogyal of Sikkim in 1835. In 1849, the British East India Company (BEIC) director Arthur Campbell and the explorer and botanist Joseph Dalton Hooker were imprisoned in the region by the Sikkim Chogyal. The East India Company sent a force to free them. Continued friction between the BEIC and the Sikkim authorities resulted in the annexation of 640 square miles (1,700 km) of territory in 1850. In 1864, the Bhutanese rulers and the British signed the Treaty of Sinchula that ceded the passes leading through the hills and Kalimpong to the British. The continuing discord between Sikkim and the British resulted in a war, culminating in the signing of a treaty and the annexation by the British of the area east of the Teesta River in 1865. By 1866, Darjeeling district had assumed its current shape and size, covering an area of 1,234 square miles (3,200 km).
During the British Raj, Darjeeling's temperate climate led to its development as a hill station for British residents seeking to escape the summer heat of the plains. The development of Darjeeling as a sanatorium and health resort proceeded briskly. Arthur Campbell, a surgeon with the Company, and Lieutenant Robert Napier were responsible for establishing a hill station there. Campbell's efforts to
