 On 12 May 1969, the minor district ("king amphoe") Chiang Mun was established as a subordinate of Pong district, consisting of the two "tambons" Chiang Muan and Sa.The third sub-district Ban Mang was established in 1970.On 1 April 1974, it was upgraded to a full district and, in 1977, it was added to newly established Phayao Province.