The diocesan territory of 1,110 square kilometres is among the four sub-divisions of Darjeeling district in West Bengal state. This area is known as the Terai plains. Siliguri is the main urban center, and a main city in West Bengal, but the diocese took the name of the smaller town of Bagdogra, which has an airport. The growing township of Siliguri has expanded into neighboring Jalpaiguri district too.
The major ethnic groups are: Bengali, Nepali, various tribal communities, Dalits, Biharis and Bhutanese. These include refugees from neighboring Bangladesh.
Major towns are: Siliguri, Bagdogra, and Matigara.
As of 2018, the total population is 1,050,000.
The main languages used are Bengali, Hindi, Oraon, Sadri, Santali, Nepali and English.
Many tribals from the Chhotanagpur area, now in Jharkhand state, in eastern India migrated here in the early 20th century to work in the tea gardens in the Darjeeling foothills. The Jesuits from Kurseong cared for the spiritual needs of these tribal migrants. The first mission station was established in Gayaganga in 1933 by Jesuit Father A. Bossaerts.
Gradually the number of Catholics and local vocations increased. To improve pastoral care for them, Bagdogra was separated from Darjeeling diocese and erected as a new diocese on June 14, 1997. Father Thomas D' Souza, the diocesan administrator of Darjeeling, was appointed its first bishop.
The Catholics are mostly tribal people originally from Chhotanagpur, primarily Oraon, Kharia, Munda, Santal and Baraik communities.
The climate is generally pleasant.
Tea gardens are a mainstay of the local economy, in which people also earn their living by cultivating rice and collecting stones to be used for road construction and railway tracks.
