1947–56

Before independence, India was divided into British-administered provinces and nominally autonomous princely states, governed by the British administration. After Indian Independence in 1947, the provinces became part of the Indian Union and the princely states who acceded were absorbed into the Union.^[5] In 1950, after the adoption of the Constitution of India, these became part of the Republic of India with the constitution classifying the states into four categories.^[6]

During the 1950–1956 period, small changes were made to state boundaries with Bilaspur merging with Himachal Pradesh on 1 July 1954 and Chandernagore, a former enclave of French India incorporated into West Bengal in 1955.^[7] In 1953, Andhra state was split from Madras state, following the death of Potti Sriramulu and the subsequent riots, demanding a separate state for the Telugus.^[8] In 1954, French enclaves of Pondichéry, Karikal, Yanaon and Mahé were transferred to India.^[7] In 1956, the States Reorganisation Act was passed, which re-organized the country into 14 states of Andhra Pradesh, Assam, Bihar, Bombay, Jammu and Kashmir, Kerala, Madhya Pradesh, Madras, Mysore, Orissa, Punjab, Rajasthan, Uttar Pradesh, West Bengal and six union territories of Andaman and Nicobar Islands, Delhi, Manipur, Tripura, Himachal Pradesh, Laccadive, Minicoy & Amindivi Islands.^[9]

1957–99

Bombay state was split into Gujarat and Maharashtra on 1 May 1960 by the Bombay Reorganisation Act.^[10] Goa, Daman and Diu was established as a union territory, following the liberation of Goa from Portuguese in 1961.^[7] In 1961, during Bengali Language Movement, protests erupted demanding a separate Barak state.^[11] Pondicherry was established as a union territory.^[7] In 1963, Naga people of undivided Assam's Naga hills demanded for a separate Nagaland state, resulting in clashes with the statehood granted on 1 December 1963.^[12] In 1966, protests erupted demanding a separate Mizo state which resulted in the bombing of Aizawl.^[13][14] The Punjabi Suba movement, which sought a separate Punjabi-speaking state, resulted in the Punjab Reorganisation Act of 1966, which created the state of Haryana and the union territory of Chandigarh with the transfer of the northern districts of Punjab to Himachal Pradesh.^[15][16][17]

Madras state was renamed as Tamil Nadu in 1969.^[18] Himachal Pradesh was elevated to statehood in 1970.^[7] The north-eastern states of Manipur, Meghalaya and Tripura were established in January 1972.^[19] Mysore State was renamed Karnataka in 1973. The Kingdom of Sikkim joined the Indian Union as a state on 26 April 1975.^[20] In February 1987, Arunachal Pradesh and Mizoram were established as new states.^[19] In May 1987, Goa achieved statehood with the northern exclaves of Daman and Diu becoming a separate union territory.^[7] The Gorkhaland movement during 1986–88, demanding a separate state resulted in violtent clashes, encounters and arrests.^[21]

2000–present

In 2000, three new states were created: Chhattisgarh from Madhya Pradesh, Uttaranchal from Uttar Pradesh and Jharkhand from Bihar.^[7] In 2006, Pondicherry was renamed as Puducherry and Uttaranchal became Uttarakhand followed by Orissa being renamed as Odisha in 2011.^[7] There have been other movements such as the Bodoland and Karbiland in Assam which have resulted in violence.^[22][23] In June 2014, Telangana was separated from Andhra Pradesh as the 29th state of the union, following the Telangana movement.^[24] On 31 October 2019, the state of Jammu and Kashmir was split into two new union territories of Jammu and Kashmir and Ladakh.^[25] On 26 January 2020, the Union Territory of Daman and Diu and the Union Territory of Dadra and Nagar Haveli were merged into a single union territory of Union Territory of Dadra and Nagar Haveli and Daman and Diu.^[26]