About the origin of the name,”Sirmour” there are quite a few surmises. One view being that the state derived its name as Sirmour because of the senior position it held amongst the princely hill states. Another version is that at the earliest times the capital of the state was at Sirmour and the state was so called after the name of the capital. But,how the word Sirmour originated is not known. Third version being that the state was founded by Raja Rasaloo of Jaisalmer whose one of the ancestor’s name was Sirmour and who belonged to Rasaloo family. Beyond this, nothing definite is traceable.One of the thakurs was was invested with the judicial and executive powers. Another thakur was given the status of a Revenue Officer. These functionaries exercised traditional as well as other power conferred by the government. The Assistant Commissioner of Kullu used to visit the area once a year for a month or so. In the late thirties the unprecedented prosperity of the people and their consequent awakening created a formidable challenge to the power and influence of the thakur of Lahaul, which gradually started declining.
The legend goes that during the earliest history of Sirmour State when Raja Madan Singh used to rule, a woman knowing necromancy presented before the Raja and talked about her acrobatic skill. Raja being susceptible about it, promised her half of his kingdom if she displayed her skill by crossing over the river Giri by means of acrobatic rope. To his surprise, she succeeded in crossing and when she was returning on the rope one of the courtiers of the Raja feeling apprehensive, cut the rope and consequently the woman was drowned in the river. This treachery on the part of Raja resulted in a flood, which swept the town, and the entire princely family perished leaving the state without a ruler.
One version goes that on this state of affairs, the subjects of the Sirmour State approached the Raja of Jaisalmer to give one of his sons as the ruler of the State, which was conceded and sent one of his sons who as crowned as Raja of Sirmour. According to another version, in about 1097 AD, Raja of Jaisalmer, Ugar Sen who happened to visit Hardwar on pilgrimage and on hearing the throne vacant in the near by state sent his son Soba Rawal who conquered and established his kingdom with the capital at Rajban taking the title of Subans Parkash. He ruled the state uptil 1099 AD and thus after 4 years of rule he expired. Ever since, the name “Parkash” in the princely family of Sirmour continued till to-day and uptil the date of lapse of paramountcy the same dynasty continued to rule Sirmour State. Malhi Parkash ruled the state from 1108 AD to 1117 AD. He was a man of deep religious and charitable disposition. He fought battle with the Raja of Sirinagar of Garhwal and wrested from him the fort of Malda. His decendant Udit Parkash ruled from 1121 to 1127 AD who changed his capital from Rajban to Kalsi in Dehra Dun otherwise his period was not much eventful. Down the decent in the line, comes the name of Somar Parkash who ruled the stae from 1149 AD to 1158 AD, who conquered the fort of Ratesh in Kenothal state and made it his capital. But, Suraj Parkash who ruled from 1158 AD to 1169 AD, returned his capital to Kalsi whereupon his subjects revolted against him and his daughter was killed in the process of defending the fort.