The Gurkhas, a martial tribe came to power in Nepal in the year 1768. They consolidated their military power and began to expand their territory. Gradually the Gorkhas annexed Sirmour and Shimla. With the leadership of Amar Singh Thapa, Gorkhas 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 Gorkhas could not capture Kangra fort which came under Maharaja Ranjeet Singh in 1809. After the defeat the Gorkhas began to expand towards the south of the state. However, Raja Ram Singh, Raja of Siba State managed to capture 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. Thus the British gradually emerged as the paramount powers. The revolt of 1857 or first Indian war of independence resulted due to the building up of political, social, economic, religious and military grievances against the British government. People of the hill states were not as politically active as the people in other parts of the country. They remained more or less inactive and so did their rulers, with the exception of Bushahr. Some of them even rendered help to the British government during the revolt. Among them were the rulers of Chamba, Bilaspur, Bhagal and Dhami. The rulers of Bushars rather acted in a manner hostile to the interests of British.
The British territories in the hill came under 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. Amongst these were the states of Kangra, Jaswan, Datarpur, Guler, Nurpur, Chamba, Suket, Mandi and Bilaspur.
After independence the Chief Commissioner's Province of H.P. came into being on 15 April 1948 as a result of integration of 28 petty princely states (including feudatory princes and zaildars) in the promontories of the western Himalaya, known in full as the Simla Hills States & four Punjab southern hill States by issue of the Himachal Pradesh Order, 1948 under Sections 3 & 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 in the Himachal Pradesh on 1 April 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 Lt. Governor was appointed. Legislative Assembly was elected in 1952. Himachal Pradesh became a Union Territory on 1 November 1956. Following area of Punjab State namely Simla, Kangra, Kulu 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 of Punjab Reorganisation Act, 1966 by the Parliament. 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. Thus Himachal emerged as the eighteenth state of the Indian Union. Now larges changes occur and spread on huge area.