Gamu was founded in December 5, 1741 as a result of the merging of the towns of Batavag (near present-day Lullutan in Ilagan) and Itugod (now barangay Lenzon).

The population problem was later partially resolved through the forced settlement of conquered tribes into the town by the Spanish.

[5] Originally part of the Cagayan Valley, Gamu was later annexed to Nueva Vizcaya when the province was established on May 24, 1856.

San Gabriel de Batauag, the first mission to Christianize the area, was established by Dominican missionaries in 1612, led by Father Luis Flores and his assistant, Fr.

However, due to grievances and maltreatment by the Spaniards, the natives of Batauag revolted, leading to the abandonment of the mission.

Pedro Jiménez, appointed as Ambassador of Peace, successfully persuaded many to settle in Cabagan and Itugod.

Consequently, the towns of Cabagan, Itugod, and Santa Rosa de Gamu-t emerged from the original seven envisioned by the mission.

Santa Rosa de Gamu-t and Our Lady of Victories of Itugod merged on December 5, 1741, due to financial constraints, with Gamu serving as the central settlement.

Barangays District I, II, and III are considered as urban (highlighted in bold) while the rest are rural.

[citation needed] Gamu is noted for having the most number of Roman Catholic churches in the entire province of Isabela.

As a municipality in the Province of Isabela, government officials in the provincial level are voted by the electorates of the town.