According to Skanda Purana, Dun formed part of the region called Kedar  Khand.

It  was included in the kingdom of Ashoka by the end of the 3rd  century  B.C.

It  is  revealed by history that for centuries the region formed part  of  the Garhwal kingdom with some interruption from Rohillas. For about two  decades till 1815 it was under the occupation of the Gorkhas.  In April 1815  Gorkhas were  ousted from Garhwal region  and Garhwal was annexed by the British.  In that  year  the  area now comprising tehsil Dehra Dun was  added  to  district Saharanpur.

240 kms from New Delhi lies the Dehradun Valley. The Valley lies between Western Himalayan ranges comprising of Chakrata, Mussoorie and Dhanaulti in the North and Shiwalik ranges in the South. In the West it is bordered by river Yamuna and in the East by river Ganges. Besides these two major rivers, the valley is well watered by many perennial streams. The area and its surrounding hills has a record of 587 bird species. Mixed forests dominated by Sal, cover most of the valley and surrounding hills. The flat stretches in the central valley is occupied by agricultural land, riverside scrubs and agro-forestry.