How Calcutta, once the capital of British empire came into being ?

Fort William, headquarters of the British East India Company en.wikipedia.org

But for the last phase  of colonial rule (about 36 years), Calcutta or Kolkata, was the second  largest city of the British Empire, a seat of power which later became a launchpad for the British to establish a string of British colonies including India. The political decision taken here by the powers-that-be not only impacted India but also many British colonies.  Being a centre of cultural assimilation and learning and a hub of commerce and trade, Kolkata is symbolic of the triumphs of British administration and frontier exploration. Because of their close association with this big city, one can confront contradictions of colonial modernity side by side with native  conservatism. As we all know, this city is made of three villages with the Hoogly river connecting them to the bay. They were nondescript in nature initially, but after a century or so became a big metropolis.

The term ''Kolkata''  is derived from ''Kolikata,'' (a Bengali word)  which is the  name of one of the three Indian villages that existed prior to the arrival of the British in this country; the other two villages being Govindapur and Sutanuti.  The present city of Kolkata is situated exactly where these villages  were located. 

City of Calcutta(Kolkata) darwin.bio.uci.edu

Archaeological  findings at  Chandraketugarh located in the northern section of Kolkata  suggest  that this region has been inhabited for about  two millennia and it implies that the settlement is not a recent one as claimed by the British who opened up job opportunities here. 

However,  according to official  historical records  the history of this huge city dates back to 1690, during  which time the British East India company had been engaged at Balasore and Hooghly in mercantile trade activities  for some time with a Firman (royal decree from the then Mogul Emperor Shahjehan (1634) at Delhi. This allowed the British company agents to build a factory in Kolkata but reside at Pipili, Odisha (Orissa).  Two years later emperor  Shahjahan's  beautiful daughter, while applying scented perfume,  her dress accidentally caught fire and she received severe burns. The emperor was very much concerned about his daughter's  appearance and worried whether she would remain disfigured for the rest of her life, He brought a British surgeon of the East India company from Surat who completely cured her burns and pain and she had begun  to lead a normal life.  Instead of fees  for the medical treatment given to the Emperor's girl, the British doctor persuaded the Mogul ruler to grant permission to the English company which was keen to expaand their trading activities in Bengal. At last the doctor succeeded in getting   permission from the emperor to build a factory at Pipili and to bring in the cargo ships through the Hoogly river for loading and unloading. The same British doctor, two years later, on request from the local ruler,  cured uncurable ailment of one of the girls in the local Nawob's family and this act of the British doctor left a good impression on the local ruler, who was acting on behalf of the Mogul ruler at Delhi. This way the English doctor was instrumental in helping the EIC  establish  factories  in Balasore and Hooghly.

After Aurangazeb became the emperor,  East India company got a special Firman to continue their trading activities. However, as the Firman had a lot of holes, the British took advantage of them and violated the trade treaty. In the wake of British company's abuse of trade treaty and breach of trust,  the Nawob of Bengal  and the dishonest company officials were frequently at loggerheads with each other. This arrogant behaviour  of the English company led to  many skirmishes between them. Job Charnock took charge of the English company at a time when their enmity with the Nabob was at peak level. Nawob's forces drove  Charnock and his men  into a forest  where survival was a tough thing. During their stay in the jungle, numerous British workers died for various reasons, the main reason being dangerous mosquito bites. This forced the Crown to blockade the Mogul's ships at some places including ships with people on the way to Mecca on pilgrimage. At last both sides were back to the table for discussion to end the violent approach. After a truce with the  Chief of British, Job Charnock, Aurangazeb finally reissued  a special Firman with no flaws. This  allowed the  British company to function in a place called ''Sutanuti'' on the banks of the Hoogly river, On August 24, 1690 British flag was hoisted on the banks of Hoogly, thus  new chapter had been  added to the Indian history which was going to change the political scene of India and also of the world. Decades later, the British economy which was in a poor state begabn to grow by  leaps and bounds. Now, the British company  had to pay the ruler just Rs. 3000.00 annualy - a paltry sum  and was fully exempted from  trade duty. The Indian traders never enjoyed these privileges.

After the death of Charnock in January, 1692, the British fortified the settlement in 1696; it became a  Presidency City in 1701 and called it  ''Fort William'' after King William III of England, To accommodate rapid growth of population, build new facilities and  extend the settlement,  the company bought  the adjacent villages Kalikata and Govindpur- from landlords (Zamindars).
Calcutta once had a huge population of Angelo Indians as inter religious marriage were common prior to 1900. It is believed that Job Charnock was the founder of Kolkata (Calcutta). Now the Calcutta High Court came up with a different ruling in 2003:
Kolkata represents an ancient site near the Kali Temple at Kalighat. It had its origin in the Maurya and Gupta dynasties and the township was in existence  long before the Delhi sultanate and the Moguls. Before the British, Portuguese and French had trading centers there, Therefore, Charnock does not take the credit of founding Calcutta. This Indian city later became a  major center  for the Indian freedom struggle and is home to numerous patriots and two Nobel laureates.
Tit bits:
 Charnokite (Hyperthene granite or pink granite): This attractive igneous rock, a variety of granite group has a large portion of Hypersthene, feldspar and quartz.  It was named by Geologist T. H. Holland in 1900 after the tombstone of Job Charnock, the founder of Calcutta, in St John's Church in Calcutta, India, which is made of this rock.
http://en.wikipedia.org/wiki/History_of_Kolkata
https://indianexpress.com/article/lifestyle/books/three-villages-and-a-city-4399505/