Solan District came into existence at the time of the reorganisation of the districts of the State on Ist September, 1972. The District was carved out of Solan and Arki tehsils of the then Mahasu district and tehsils of Kandaghat and Nalagarh of the then Shimla District. Administratively, the district is divided into four Sub-division viz. Solan comprising of Solan and Kasauli tehsils, Nalagarh covers the juridisdiction of Arki and Kandaghat Sub-divisions covers their respective tehsils. The total geographical area of the district according to the Surveyour General of India is 1,936 sq. km. which constitutes 3.49 percent of the total area of the State and ranks 9th amongst the district.
The District is bounded by Shimla district in the North and by Ropar District of Punjab and Ambala district of Harayana in the south, by Sirmaur District in the east and by Bilaspur district in the west. Mandi District touches the boundary of Solan district in norht-east. The shape of the district is rectangualar with slight bulge on the northern side intruding towards Mandi district.It is located between the longitudes 76.42 and 77.20 degree and latitudes 30.05 and 31.15 degree north. the elevation of the district ranges from 300 to 3,000 metres above eas level. The mountain ranges lie in the outer Himalayas and are a part of Shivalik ranges. The mountains of lower elevation are found in western-southern parts of the distict comprising of Nalagarh and Arki tehsils while higher ranges start from central region and extend upto north-estern corner of the District comprising Solan tehsil and parts of Arki tehsil, Kasauli tehsil and Kandaghat tehsil which are located in north-eastern direction of the district and are having the highest ranges of the District.
The district in its present form comprises of the erstwhile princely states of Bhagal, Bhagat, Kunihar, Kuthar, Mangal, Beja, Mahlog, Nalagarh and parts of Keonthal and Kothi and hilly areas of composite Punjab State which were merged in Himachal Pradesh on the Ist November, 1966 on the reorganisation of composite Punjab on the linguistic basis. Most of these princely state as per history were subjected to the onslaught of Gorkha invasion from the year 1803 to 1805. it was in the year 1815 that after th gorkhas lost to the Britishers, these states were freed and restored tot he respective rulers. Most of the states were small in area and population and were under the control of the superintendent of Shimla Hill States before Independence. Himachal Pradesh appreared on the administrative map of the country on the 15th April, 1948 and the states of Bhagat, Baghal, Kunihar, Kuthar, Mangal, Beja, Keonthal and Koti formed a part of the then Mahasu District. Nalagarh state which was merged after Independence in Patiala and East Punjab State Union later on formed a part of Punjab when the reorganisation of the states took place in 1956 and remained a tehsil of Ambala District, Kandaghat and Shimla tehsils of Shimla district like othe rhilly areas of Kullu, Lahul and Spiti and Kangra districts become part of Himachal Pradesh on the Ist November, 1972 and Solan District sprang up on the administrative map of the state
Solan District derives its name from Solan town which came into existence after the construction of the Cantonment at that palce around the last quarter of the 19th century