In a land area of 14,945 square kilometers, the dicoese of Lang Son - Cao Bang comprises the three provinces of Cao Bang, Ha Giang and Lang Son.
End of 2009, the total population of the diocese was 1,645,000. The diocese is home to various ethnic groups of Cao Lan, Dao, Hmong, Nung, Kinh, San Chi and Tay living together in harmony.
Vietnamese is the main and official language in the area. Other ethnic languages are used within their communities.
Lang Son Cao Bang Vicariate was established on Dec. 30, 1913. French Dominicans started the pastoral activities.
In 1954, when French troops were defeated by communists in Dien Bien Phu battlefield, 2,500 people accounting for half of the vicariate's Catholic population moved to the south to avoid religious persecution. They left four French clergy and four Vietnamese priests serving local people at 11 parishes and 14 churches. Before the exodus, the vicariate had 26 parishes and 26 churches.
After French clergy were expelled from the country or died, Father Vincent Pham Van Du was named bishop of the diocese in 1960 but his episcopal ordination was in 1979 in Bac Ninh diocese.
Many Church facilities including the cathedral were collapsed or damaged during the Vietnam War and Vietnam-China War in 1979.
Bishop Du moved to Lang Son City in 1990 after he was isolated at That Khe Church for 31 years. He built the Bishop's House and two churches before he died in 1998 and left one elderly priest to the diocese.
Bishop Joseph Ngo Quang Kiet became bishop of the diocese in 1999. He built the Cathedral and some Church facilities before he became archbishop of Ha Noi in 2007.
Now, Bishop Joseph Dang Duc Ngan, the third Vietnamese prelate of the diocese, and local Catholics try to train missioners and provide faith education for people.
Lang Son - Cao Bang diocese is one of nine suffragans of Ha Noi Archdiocese. Its titular is the feast of Saint Dominic, August 8.
Roads and railways mainly link areas in the diocese. There are two border crossings between Vietnam and China by train and bus in Lang Son province and seven markets nearby the border between the two countries. Various goods from China are illegally transported into the country through those places.
Categorized as the transitional climate between subtropical zone and warm temperate zone, Lang Son - Cao Bang features clearly demarcated seasons, sufficient rainfall and plentiful sunlight. The average temperature is 17 to 22 degrees Celsius year-round. The annual average rainfall is 1,200-1,600 millimeters and the average sunshine is 1,600 hours year-round.
Most of local people are dependent on agriculture for their livelihood. Major agricultural crops grown are rice, corn, root vegatables, beans and fruit trees. Many people also raise honey bees and collect and gather fruits in forest for a living.
The diocese is home to many ethnic groups who own various indigenous cultures. o Cho Tinh Khau Vai or Market of Love in Khau Vai is held once a year and gives opportunities for men and women who could not get married.