Sadanga is a sleepy town which befits its name Sadanga romanticized by young researchers to have been derived from the combination of English word “sad” and its local meaning “sanga.” Some youths still call the place Sadsanga though Sadanga is the proper name.
Sadanga was once a municipal district, during the old Mountain Province which included the present Mountain Province, the provinces of Benguet, Abra, Kalinga-Apayao, and Ifugao. The municipal district was then comprised of five barangays- Bekigan, Belwang, Saclit, Sacasacan and Sadanga.
On October 14, 1949, Barangays Anabel and Betwagan were added to the municipal district pursuant to Resolution No. 592 of the Provincial Board of the old Mountain Province which increased its barangay to Seven barangays.
On June 25, 1963, President Diosdado Macapagal signed Executive Order No. 42 that converted 57 municipal districts, including Sadanga, into regular 5th class municipalities.
Sacasacan was then the first seat of government until 1939 when the Americans transferred it to Koprew, one of the sitio of what is popularly known as Sadanga.
In July 30, 1995, Provincial Ordinance No. 2 was issued dividing a place popularly known as Sadanga into two barangays. The seat of modern government was named Poblacion while the powerful seat of culture and indigenous governance was named Demang. This finally relinquished the name Sadanga to mean the name of the municipality.
It was reclassified from Sixth class municipality to fifth class municipality by the Bureau of Local Government Finance under BLGF-MC-97-3(47) and now Municipal Government derives its mandate from RA 7160 approved in 1991.