On 17, October, 1961 the foundation of Darkhan city was laid in economically favourable land of Darkhan sum of Selenge aimag. The sum was abolished and began to be administered by Darkhan Administration in 1963. Joint-ventures set up by assistance of socialist countries in Darkhan in 1970-1990 played significant role in becoming a highly industrialised region of Mongolia. The aimag ranked third in the sale of industrial products in 1997. As of the beginning of 2005, total livestock is 125.1 thousand heads. Previously Darkhan aimag was a part of Selenge aimag so the biodiversity and climate are almost the same. 76% of the population of Darkhan-Uul aimag live in Darkhan City and 86% of them live in residential apartments.