in 1947 the Punjab Province of British India

in 1947 the Punjab Province of British India was partitioned along religious lines into West Punjab and East Punjab. Huge numbers of people were displaced, and there was much intercommunal violence. Following independence, several small Punjabi princely states, including Patiala, acceded to the Union of India and were united into the PEPSU. In 1956 this was integrated with the state of East Punjab to create a new, enlarged Indian state called simply "Punjab".
The undivided Punjab, of which Pakistani Punjab forms a major region today, was home to a large minority population of Punjabi Hindus and Sikhs until 1947, apart from the Muslim majority.[32]
Immediately following independence in 1947, and due to the ensuing communal violence and fear, most Sikhs and Punjabi Hindus who found themselves in Pakistan migrated to India as part of the exchange of populations.[33] Punjabi Muslims were uprooted similarly from their homes in East Punjab, which now forms part of India.[34] More than seven million moved to Pakistan, and over six million settled in Punjab.
In 1950, two new states were recognised by the Indian constitution: the Indian part of the former British province of Punjab became the state of East Punjab, while the princely states of the region were combined into the Patiala and East Punjab States Union (PEPSU). Himachal Pradesh was later created as a union territory from several princely states in the hills The capital city of the undivided Province of Punjab, Lahore, was allocated to the Pakistani West Punjab during the partition of British India in 1947, so a new capital for Indian Punjab was built at Chandigarh. Shimla was named temporary capital of the Punjab until Chandigarh was completed in 1960.
After years of protest by Akali Dal and other Sikh organisations, finally Punjab was divided on a linguistic basis in 1966. On 1 November 1966, the Hindi-speaking southern half of Punjab became a separate state, and Haryana and the Pahari-speaking hilly areas in the north became Himachal Pradesh. Chandigarh was on the border between Punjab and Haryana and became a union territory that serves as the capital of both Punjab and Haryana. During the 1970s, the Green Revolution brought increased economic prosperity for the Punjab, mainly due to the late Pratap Singh Kairon. However, a growing polarisation between the Indian National Congress central government and the main Sikh political party, the Shiromani Akali Dal, developed during the 1970s. Hostility and bitterness arose from what was widely seen by the Akali Dal as increasing alienation, centralisation and discriminatory attitudes towards Punjab by the Government of India. This prompted the Shiromani Akali Dal to pass the Anandpur Sahib Resolution, which asked for granting maximum autonomy to the region of Punjab and other states and limited role and powers of the Central Government.