From the Wikipedia page 
Sông Bé was a province in southern Vietnam, which borders Cambodia to the north, Lâm Đồng to the east, Đắk Nông to the northeast, Hồ Chí Minh City to the south and Tây Ninh to the west.
Sông Bé was formed in 1976 in merge of three previous provinces, Bình Dương, Phước Long and Bình Long. Its capital was at Thủ Dầu Một. In 1995 it had area of 8519.4 km² and population of 1081700. On 1 January 1997 it was again split into two provinces, Bình Dương and Bình Phước.
The separation revealed the regional inequality within the former province: While Bình Dương is one of the most industrialised provinces in southern Vietnam, Bình Phước is one of the least industrialised - in the late 1990s even less industrialised than the provinces of the Central Highlands. However, the gap between the two provinces has diminished gradually since separation in relatively terms.