The history of the area that now constitutes Himachal Pradesh dates to the Indus valley civilisation that flourished between 2250 and 1750 BCE. Tribes such as the Koili, Hali, Dagi, Dhaugri, Dasa, Khasa, Kinnar, and Kirat inhabited the region from the prehistoric era.
During the Vedic period, several small republics known as Janapada existed which were later conquered by the Gupta Empire. After a brief period of supremacy by King Harshavardhana, the region was divided into several local powers headed by chieftains, including some Rajput principalities. These kingdoms enjoyed a large degree of independence and were invaded by Delhi Sultanate a number of times. Mahmud Ghaznavi conquered Kangra at the beginning of the 10th century. Timur and Sikander Lodi also marched through the lower hills of the state and captured a number of forts and fought many battles. Several hill states acknowledged Mughal suzerainty and paid regular tribute to the Mughals.
The Kingdom of Gorkha conquered many kingdoms and came to power in Nepal in 1768. They consolidated their military power and began to expand their territory. Gradually, the Kingdom of Nepal annexed Sirmour and Shimla. Under the leadership of Amar Singh Thapa, the Nepali army laid siege to Kangra. They managed to defeat Sansar Chand Katoch, the ruler of Kangra, in 1806 with the help of many provincial chiefs. However, the Nepali army could not capture Kangra fort which came under Maharaja Ranjeet Singh in 1809. After the defeat, they began to expand towards the south of the state. However, Raja Ram Singh, Raja of Siba State, captured the fort of Siba from the remnants of Lahore Darbar in Samvat 1846, during the First Anglo-Sikh War.
They came into direct conflict with the British along the tarai belt after which the British expelled them from the provinces of the Satluj. The British gradually emerged as the paramount power in the region. In the revolt of 1857, or first Indian war of independence, arising from a number of grievances against the British, the people of the hill states were not as politically active as were those in other parts of the country. They and their rulers, with the exception of Bushahr, remained more or less inactive. Some, including the rulers of Chamba, Bilaspur, Bhagal and Dhami, rendered help to the British government during the revolt.
The British territories came under the British Crown after Queen Victoria's proclamation of 1858. The states of Chamba, Mandi and Bilaspur made good progress in many fields during the British rule. During World War I, virtually all rulers of the hill states remained loyal and contributed to the British war effort, both in the form of men and materials. Among these were the states of Kangra, Jaswan, Datarpur, Guler, Rajgarh, Nurpur, Chamba, Suket, Mandi, and Bilaspur.
After independence, the Chief Commissioner's Province of Himachal Pradesh was organized on 15 April 1948 as a result of integration of 28 petty princely states (including feudal princes and zaildars) in the promontories of the western Himalayas. These were known as the Simla Hills States and four Punjab southern hill states under the Himachal Pradesh (Administration) Order, 1948 under Sections 3 and 4 of the Extra-Provincial Jurisdiction Act, 1947 (later renamed as the Foreign Jurisdiction Act, 1947 vide A.O. of 1950). The State of Bilaspur was merged into Himachal Pradesh on 1 July 1954 by the Himachal Pradesh and Bilaspur (New State) Act, 1954.
Himachal became a Part 'C' state on 26 January 1950 with the implementation of the Constitution of India and the Lieutenant Governor was appointed. The Legislative Assembly was elected in 1952. Himachal Pradesh became a union territory on 1 November 1956. Some areas of Punjab State— namely Simla, Kangra, Kullu and Lahul and Spiti Districts, Nalagarh tehsil of Ambala District, Lohara, Amb and Una kanungo circles, some area of Santokhgarh kanungo circle and some other specified area of Una tehsil of Hoshiarpur District, besides some parts of Dhar Kalan Kanungo circle of Pathankot tehsil of Gurdaspur District—were merged with Himachal Pradesh on 1 November 1966 on enactment by Parliament of Punjab Reorganisation Act, 1966. On 18 December 1970, the State of Himachal Pradesh Act was passed by Parliament, and the new state came into being on 25 January 1971. Himachal became the 18th state of the Indian Union with Dr. Yashwant Singh Parmar as its first chief minister.