Besides the Union Territory of Chandigarh, the diocese consists of eight civil districts in Himachal Pradesh, 12 civil districts of Haryana and six civil districts of Punjab, spread in an area of 83, 560 square kilometers.
Tribals and Dalits populate in many villages. Most of the people are engaged in farming. They cultivate rice, wheat, vegetables, apples, etc. Many industries and business centers are situated in urban areas. Many areas of the diocese are mountainous.
The diocese has many important national tourism centers like Shimla, Kullu, Mandi, Mohali, Kurukshetra, Panipat, besides the new city of Chandigarh.
Simla - Chandigarh diocese has a long history. Dividing the area from Agra archdiocese, the mother of all dioceses in North India, Simla archdiocese was created in 1910, with Archbishop Anselm E.J. Keneally, OFM Cap, as its first archbishop.
When Delhi became the capital of the independent India, the See was shifted to Delhi and was known as Delhi-Simla archdiocese. Archbishop Sylvester P. Mulligan became its first archbishop.
In 1959 Delhi was dismembered and Simla became an independent diocese, with Bishop John Burke heading it.
With the formation of the new city of Chandigarh, the socio - political life of the people centered around this new city and so the bishop was forced to remain in Chandigarh, though Simla remained its headquarters. It was Bishop Gilbert Blaize Rego finally shifted the residence to Chandigarh and the diocese was known as Simla-Chandigarh diocese.
The Catholic community consists of various ethnic, linguistic, socio, economic and cultural groups. Besides the pastoral care of the Catholics, the Catholic Church is engaged in serving the people through various educational and social activities.
Most of the people are Hindus. Being the home of Sikhism, Sikhs form the second majority and the Muslims form the third. Other Christian denominations are also active in the area.