The St. John’s Church is the third oldest church of Kolkata. It lists among the important heritage sites of Kolkata. An original Parish Church of Bengal, it became the principal Cathedral of Calcutta in 1815 and remained so until the consecration of St. Paul’s Cathedral in 1847. A part of the premise on which the church stands now was originally a cemetery.
To the east of this burial ground, there was an 'Old Powder Magazine Yard' or simply a storage tank for gun powder during the invasion of Nawab Siraj-ud-Daulah in 1756. The tank was a massive circular brick erection of sixty feet diameter, remaining unused since the invasion. Together with an approximate hundred square feet tank nearby, the magazine yard was privately auctioned by the Company on 11th January 1774 and purchased by Raja Nabakrishna Deb of Sobhabazar Deb family. Raja Nabakrishna 'presented' this same property to Warren Hastings (against consideration of 10000 rupees as per Cotton) in December 1783, for the construction of the Church, who in turn offered it to the building committee or the Church committee. The construction started in 1784.
The St. John’s Church was built in 1787 by architect James Agg. The model for St. John's was the St. Martin-in-the-fields of London, designed by James Gibbs in 1726, which was a prototype for building English churches then. But Lt. Agg had to make some modifications in the design to accommodate for the soft ground.
The construction and the arrangement for it was a collective effort. Sandstone from Chunar was used for the Steeple and the Spire. Capt. Caldwell dispatched the stones from the quarries at Chunar while Mr. Wilkins supervised the molding of the stones at Benaras. Blue Marbles from the ruins of Gour (the stones were finely polished as per the records), which were already removed from the Gour's tombs in 1768-69 by Major Adams during survey work, were used for Church pavements. Mr. Grant superintended the supply of marbles from Malda to Calcutta. The extensive use of stones earned the Church its native nickname 'Pathure Girja' or Stone Church. The architectural design of the church was made in accordance with the design of St. Martin’s Church, London.
The single-spire Gothic church is built entirely of stone and its original construction is left virtually untouched till date. The steeple and porticos have grand Doric columns. The floor of the church is paved with slabs of blue-grey or black marble. These slabs came from the ruins of Gour in Malda district.
The 174 feet tall clock bell tower is made of stone from Chunar and there is magnificent teakwood furniture in the church and a grand old pipe organ which is still played during the Sunday service.
Of the old mausoleums, only those of Charnock and Admiral Waton (who, with Robert Clive, liberated Calcutta from Siraj-ud-Daula. He provided transport for Clive and his forces up the river Hooghly and then supported them in the repossession operation) were left undisturbed. The other graves were dug up and the remains were taken away.
Another monument of prime importance in the courtyard of the church is the (in)famous Black Hole Monument.
The interior of the church is decorated with beautiful wood carvings and marble bass relief work. The windows of the church are built with color stained glasses. On its walls hangs the large painting of ‘The Last Supper’ which John Zoffany presented to the church.
Within the Altar, on the left, there is the old but still smoothly functioning Pipe Organ. The Organ predates the Church and has 1500 pipes. It was originally inside the St. Mary's Church of Fort St. George, Madras, the oldest Anglican Church of India. When French occupied Madras during 1746-49, they took away the Organ to Pondicherry. It was retrieved in 1761 by the British, by capturing the French base of South India. But by then, a new instrument was already in the place at St. Mary's so it was kept in storage and later sent to Calcutta when St. John's was constructed.