The Church of South India, generally known as the CSI, is the union of three major church groups – the South India United Church (SIUC) containing both Presbyterian and Congregational elements, the Methodists, and the Anglicans. This union was established on 27 September, 1947, when their representatives met in the St. George Cathedral, Madras.  Bishop C.K. Jacob, an ex-Anglican  of the Central Travancore Diocese of the SIUC, under whose leadership this union took place, declared at that time, that “the Church of Madras, Travancore-Cochin, Tinnevely and Dornakal dioceses of the Church of India, Burma and Ceylon, and the Madras, Madera, Malabar , Jaffna, Kannada, Telugu and Travancore Church Councils of the South India United Church, and the  Methodists Church of South India comprising the Madras, Trichinapoly,  Hyderabad and Mysore districts have become one Church of South India”. The CSI thus occupies that part of the South Indian peninsula within the states of Madras, Mysore, Andhra Pradesh and Kerala, and Jaffna and Sri Lanka.  The missionary societies that worked in these regions were the London Missionary Society (LMS) in the South Travancore, the Church Missionary Society (CMS) in the Central Travancore, the Anglican Societies in the old Tinneveli district, the Dutch Reformed Church of America in the old Arcot district, the Church of England Zenana Missionary Society, the Church of Scotland Foreign Mission Committee, the Methodist Missionary Society of Britain, the American Board of Commissioners of Foreign  Missions  (Boston of America), the Society for the Propagation of the Gospel in Foreign Parts, and the Evangelical Missionary Society (E.M.S.), Germany. 

In Kerala, particularly, the CSI church is an amalgamation of the erstwhile South India United Churches (SIUC) which was formed in 1907 and the former Anglican Diocese of Travancore and Cochin that was founded in 1879. Historically, the London Missionary Society (LMS) commenced its work in South Travancore in 1806. Vedamanickanm Maharasan Desikar was the first Christian who invited William Tobias Ringeltauble, the first missionary to come to Travancore. When the SIUC was formed in 1907 with 9 member church denominations the South Travancore LMS Church was an important constituent. In 1921 the South Travancore Church Council was constituted with the Tamil and Malayalam churches of the SIUC having put together. In the North Kerala there was the Anglican Diocese of Travancore and Cochin under the Rt. Rev. C.K. Jacob, the first Indian bishop of the diocese who was also the presiding bishop at the time of the inauguration of the CSI union. This diocese was originally the work of the CMS Missionaries the first of whom arrived in Travancore in 1816 primarily as a Mission of Help to the members of the ancient Syrian Church.  They soon got separated from their Jacobite/Orthodox church and formed the Anglican Church.  A few years later, there arose a great mass movement among the outcast people in Central Travancore and this section soon became the majority community of the Central Travancore Diocese of the Anglican church that joined the CSI union and  became the CSI Madhya Kerala Diocese. But a good proportion of leadership of this community has been from the Syrian group who claim the St. Thomas tradition.

One of the important characteristics of the CSI union was the acceptance of the three different traditions: Episcopacy, Ordination, and Church government. As such it has a blend of elements of the Presbyterians, the Congregationalists, and the Protestants. The CSI has a democratic set up with the ‘Synod’, the ‘Diocesan Council’, and the ‘Pastoral Committee’. When formed in 1947 CSI had 14 dioceses including the 3 in Kerala area. After 50 years, it has grown into 21 Dioceses with the 4 in Kerala, namely, the East Kerala Diocese (Melukavu), the Madhya Kerala Diocese (Kottayam), the North Kerala Diocese (Shoranur), and the South Kerala Diocese (Thiruvananthapuram). The church is governed by a Synod at Chennai and headed by a Bishop who is elected once in two years.

References:
1. GEORGE, K.M. Church of South India Life in Union (1947-1997), Delhi, ISPCK/CSS, 1999; 292 pp.
2. PAUL CHIRAKKARODU. Dalith kraisthavar kerathil, Tiruvalla, Christwawa Sahitaya Samithy, 2001, 246 pp.)