The mother town of Sison is San Fabian. Bulaoen was formerly a big barrio of San Fabian in its eastern part. This barrio became a municipality named Alava in 1862 as a result of the petition of its residents dated December 15, 1862. Afterwards, its poblacion was moved to its present site.
About the year 1907, the township of Esperanza, northeast of Alava, was organized comprising the barrios of Pinmilapil, Agat, Sagunto, Cauringan, Bila and Colisao (now belonging to San Fabian). The same year, the township of Labayug, northeast of Pozorrubio was also organized, comprising Inmalog, Calunetan, San Andres, Alibeng , Bacayao and Killo.
Later, these two townships (Esperanza and Labayug) fused together to form the township of Artacho, making the present barrio of Artacho as its poblacion. The former town of Alava had been in a move to expand its jurisdiction. The township of Artacho had also a move to become a regular municipality. As a result of their efforts, they fused as one.
Incidentally, this fusion was sponsored by the late Senator Pedro Ma. Sison in the senate. When approved by congress, the late Governor Wood decreed that the fusion be made on May 11, 1918 and the town was named SISON after its sponsor, Senator Sison.