Langfang, is a prefecture-level city of Hebei Province, which was known as Tianjin Prefecture until 1973. It was renamed Langfang Prefecture after Tianjin became a municipality and finally upgraded into a prefecture-level city in 1988. Langfang is located approximately midway between Beijing and Tianjin. At the 2010 census, the population of Langfang was 4,358,839, of whom 868,066 lived in the built-up (or metro) area made of Guangyang and Anci districts; its total area is around 6417.28 km². Langfang borders Baoding to the southwest, Cangzhou to the south (both prefecture-level cities of Hebei), Beijing to the north and Tianjin to the east. Sanhe City and Dachang Hui County are now conurbated with Beijing, so that they form part of the same built-up area. Langfang is the smallest prefecture-level city of Hebei Province by land area.