DEHRA DUN, a district of British India, in the Meerut division of the United Provinces, with an area of about 1,189 sq.m. The Dun proper is a beautiful valley lying between the Siwalik range and the foot-hills of the Himalayas. The administra tive district runs up into the latter and embraces the sanatorium of Mussoorie. The mountains in its northern section attain a height between 7,00o and 8,000 ft., one peak reaching an elevation of 8,565 ft.; the highest point of the Siwalik range is 3,041 ft. above sea-level. The principal passes through the Siwalik hills are the Timli pass, leading to the military station of Chakrata, and the Mohand pass leading to the sanatoriums of Mussoorie and Landaur. The Ganges bounds the Dehra valley on the east; the Jumna bounds it on the west. It is well wooded, undulating, and relatively temperate in climate. To the east the valley is charac terized by swamps and forests, but to the west the natural de pressions freely carry off the surface drainage. In 1931 the popu lation was 230,247. A railway to Dehra from Hardwar, on the Oudh and Rohilkhand line (32 m.) , was completed in 1900. The district is served by the Dun canals. Tea gardens cover a con siderable area, and the valley contains a colony of European tea planters.
Dehra Dun only emerges from the mists of legend into authentic history in the 17th century A.D., when it formed part of the Garhwal kingdom. Towards the end of the century the heretical Sikh Guru, Ram Rai, expelled from the Punjab, sought refuge in the Dun and gathered a crowd of devotees. Fateh Sah, raja of Garhwal, endowed the temple which he built, round which grew up the town of Gurudwara or Dehra (q.v.). In the 18th century the fertility of the valley attracted the attention of Najib-ud-daula, governor of Saharanpur, who invaded it with an army of Rohillas in 1757 and annexed it to his dominion. His rule, which lasted till 17 7o, brought great prosperity to the Dun; but on his death it became a prey to the surrounding tribes, its desolation being completed after its conquest by the Gurkhas in 1803. In 1814 it was taken possession of by the British.