Formation of States in India in chorological order:
1902: Name of North Western Provinces and Oudh changed to United Provinces of Agra and Oudh.
1902-10-01: Berar merged with Central Provinces to form Central Provinces and Berar.
1905-10-16: Bengal and Assam provinces reorganized into Eastern Bengal and Assam province and West Bengal province.
1910: Native state of Benares formed by merging a number of smaller fiefs.
1911-12-12: 1905 partition of Bengal was nullified.
1912-10-01: Delhi province split from Punjab; Indian capital moved from Calcutta to Delhi.
1912: Bihar and Orissa province split from Bengal.
1931-02-10: New Delhi officially replaced Delhi as capital.
1932: Aden province split from Bombay presidency.
1935: Name of United Provinces of Agra and Oudh changed to United Provinces.
1936-04-01: Orissa province formed from parts of Bihar and Orissa province, Central Provinces and Berar province, and Madras presidency; remaining part of Bihar and Orissa renamed Bihar; status of Sind division of Bombay presidency changed to province.
1937-04-01: Aden (now in Yemen) and Burma (now Myanmar) split from India as crown colonies.
1947-08-15: Indian independence. The British provinces became part of India immediately. The native states and agencies became effectively independent. Some of them were allowed to decide whether to accede to (merge with) India or Pakistan. Others combined to form new states in the Indian Union, or merged directly with existing provinces. The process was essentially complete when the new Constitution took effect, less than 2 1/2 years later. On this date, Bengal split into West Bengal (India) and East Pakistan; Punjab split into East Punjab (India) and West Punjab (Pakistan); the presidency of Bombay, which had consisted of Bombay and Sind provinces, split, with Sind going to Pakistan; Banaras, Rampur, and Tehri-Garhwal states merged with United Provinces; Central Provinces and Berar became Madhya Pradesh.
1947-10: France ceded its loges, the sites of French-owned factories (trading posts) in Bombay, Madras, and Orissa provinces, totaling 526 sq. km., to India.
1947-10-26: Jammu and Kashmir state became part of India by the signing of the Instrument of Accession. However, Pakistani fighters invaded the area, bringing about a de facto partition which has been in dispute ever since.
1947-11-08: India annexed the native states of Junagadh and Manavadar to Rajputana, even though they had acceded to Pakistan.
1948: Native states merged to form seven unions: Greater Rajasthan (corresponding to an area called Rajputana before independence), Madhya Bharat (also called the Malwa Union), Patiala and East Punjab States Union (PEPSU for short), Saurashtra (also called the United State of Kathiawar), Travancore-Cochin, United Deccan State, and Vindhya Pradesh.
1948: 15 native states merged with Madhya Pradesh.
1948: Native states of Banganapalle and Pudukottai merged with Madras state.
1948: 174 native states merged with Bombay, including Baroda, Cambay, Idar, Janjira, Kolhapur, Palanpur, Radhanpur, Rajpipla, Sirohi, and the states of the United Deccan State.
1948: Native states of Dujana, Loharu, and Pataudi merged with East Punjab.
1948-04-15: Himachal Pradesh state formed from 30 former Hill States, including Chamba, Mandi, Nahan, Sirmur, and Suket.
1948-05: Native states of Saraikela and Kharsawan merged with Bihar.
1949-04-01: Native state of Sandar merged with Madras state.
1949-08-01: 24 former native states merged with Orissa.
1949-10-15: Tripura merged with India as a centrally administered area.
1949-10-15: Manipur merged with India as a union territory.
1950-01-01: Cooch Behar state merged with West Bengal.
1950-01-24: Name of United Provinces changed to Uttar Pradesh.
1950-01-26: The Constitution took effect. The divisions of India were classified as follows: nine Part A states, formerly governors' provinces; eight Part B states, formerly native states or groups of states; ten Part C states, formerly chief commissioners' provinces; and two Part D territories. Name of East Punjab state changed to Punjab (India). Greater Rajasthan union became Rajasthan state.
1950-05-02: Chandernagore transferred from French possession to India.
1950-12-05: Sikkim became an Indian protectorate.
1951: Territory in Assam around Dewangiri ceded to Bhutan.
1953-10-07: Capital of Punjab moved to the new city of Chandigarh.
1953-10-01: Andhra Part A state split from Madras.
1954: Bilaspur state merged with Himachal Pradesh.
1954-10-02: Chandernagore merged with West Bengal.
1956: Capital of Hyderabad moved from Kurnool to Hyderabad.
1956-05-28: France ceded Pondicherry to India as a union territory.
1956-09-01: Status of Tripura changed from centrally administered area to union territory.
1956-11-01: States Reorganization Act took effect. The distinction among Part A, B, and C states was abolished. States were reorganized largely on linguistic lines. Andhra Pradesh state formed by merging Andhra with part of Hyderabad. Bombay state formed by merging Kutch, Saurashtra union, and part of former Bombay state. Status of Delhi and Himachal Pradesh changed from states to union territories. Kerala state formed by merging most of Travancore-Cochin union and part of Madras. Laccadive, Minicoy, and Amindivi Islands union territory split from Madras. Madhya Pradesh state formed by merging Bhopal and Vindhya Pradesh union, all of Madhya Bharat union but one exclave, most of former Madhya Pradesh, and an exclave of Rajasthan. Madras state lost large areas to other states, but gained part of Travancore-Cochin union. Mysore state formed by merging Coorg and former Mysore states and parts of Bombay, Hyderabad, and Madras states. Punjab state formed by merging Patiala and East Punjab States Union and former Punjab. Rajasthan state gained Ajmer state and small parts of Bombay and Madhya Bharat union, and lost an exclave to Madhya Pradesh. 8,177 sq. km. transferred from Bihar state to West Bengal.
1957-12-01: Naga Hills-Tuensang Area split from Assam as a centrally administered area.
1960-04-01: Madras state ceded 573 sq. km. of territory to Andhra Pradesh in exchange for another territory of 1,062 sq. km.
1960-05-01: Bombay state split into Gujarat and Maharashtra by the Bombay Reorganization Act. Maharashtra also incorporated part of Madhya Pradesh and all that remained of Hyderabad state.
1961-08-11: Dadra and Nagar Haveli, formerly a Portuguese colony and independent since 1954-07, merged with India as a union territory.
1961-12-20: Portuguese India (India Portuguesa, later called Estado da India) annexed by India and became the territory of Goa, Daman and Diu.
1963-12-01: Naga Hills-Tuensang centrally administered area became Nagaland state.
1966-11-01: By the Punjab Reorganization Act, Punjab state split into a smaller Punjab state, a new Haryana state and Chandigarh union territory, and a section which merged with Himachal Pradesh. Chandigarh, formerly capital of Punjab, became joint capital of Punjab and Haryana states and its own union territory.
1968-08: Name of Madras state changed to Tamil Nadu.
1970: Capital of Gujarat moved from Ahmedabad to Gandhinagar.
1971-01-25: Status of Himachal Pradesh changed from union territory to state.
1972-01-20: Arunachal Pradesh union territory, Meghalaya state, and Mizoram union territory split from Assam; capital of Assam moved from Shillong to Dispur. Before the split, Arunachal Pradesh had been the North East Frontier Agency, and Mizoram had been the Lushai Hills district.
1972-01-21: Status of Manipur and Tripura changed from union territories to states.
1972-12-17: A new line of control between India and Pakistan in the area of Jammu and Kashmir took effect.
1973-11-01: Name of Mysore state changed to Karnataka; name of Laccadive, Minicoy, and Amindivi Islands union territory changed to Lakshadweep.
1974-05-27: Capital of Arunachal Pradesh moved from Shillong (in Meghalaya) to Itanagar.
1975-04-26: Status of Sikkim changed from protectorate to state.
1985-07-24: By the Punjab Accord, Chandigarh union territory would eventually merge with Punjab state. This has not yet been carried out, but it remains a live issue.
1986-07: Status of Mizoram changed from union territory to state.
1987-02-20: Status of Arunachal Pradesh changed from union territory to state.
1987-05-30: Goa, Daman, and Diu union territory split into Goa state and Daman and Diu union territory.
1992-02-01: Official name of Delhi union territory changed to National Capital Territory.
1996: Name of the capital of Tamil Nadu state changed from Madras to Chennai; name of the capital of Maharashtra state changed from Bombay to Mumbai.
~1996: Name of the capital of Himachal Pradesh state changed from Simla to Shimla; name of the capital of Kerala state changed from Trivandrum to Thiruvananthapuram.
1999-07-20: Assembly of West Bengal resolved to change the name of the state to Bangla, but this change doesn't take effect until passed by Indian Parliament.
2000-11-01: Chhattisgarh state split from Madhya Pradesh (former FIPS code IN15), as provided by the Madhya Pradesh Reorganization Bill, which passed on 2000-07-31. Chhattisgarh comprises sixteen districts of Madhya Pradesh: Bastar, Bilaspur, Dantewada, Dhamtari, Durg, Janjgir, Jashpur, Kanker, Kawardha, Korba, Koriya, Mahasamund, Raigarh, Raipur, Rajnandgaon, and Surguja.
2000-11-09: Uttaranchal state split from Uttar Pradesh (former FIPS code IN27), as provided by the Uttar Pradesh Reorganization Bill, which passed on 2000-08-01. Uttaranchal comprises thirteen districts of Uttar Pradesh: Almora, Bageshwar, Chamoli, Champawat, Dehradun, Haridwar, Nainital, Pauri Garhwal, Pithoragarh, Rudra Prayag, Tehri Garhwal, Udham Singh Nagar, and Uttarkashi.
2000-11-15: Jharkhand state split from Bihar (former FIPS code IN04), as provided by the Bihar Reorganization Bill, which passed on 2000-08-02. Jharkhand comprises eighteen districts of Bihar: Bokaro, Chatra, Deoghar, Dhanbad, Dumka, East Singbhum, Garhwa, Giridih, Godda, Gumla, Hazaribagh, Koderma, Lohardaga, Pakur, Palamau, Ranchi, Sahibganj, and West Singbhum. Ranchi, formerly the summer capital of Bihar, became the capital of Jharkhand.
2001-01-01: Name of the capital of West Bengal changed from Calcutta to Kolkata.
2006-09-20: Name of Pondicherry union territory changed to Puducherry.
2007-01-01: Name of Uttaranchal state changed to Uttarakhand