Reina Mercedes was founded in 1743 as the settlement of Abbag, which means "on the other side" (of the Magat River), before then being renamed to Calering, and Calanusian (from canusi, a species of white ebony).

[6] The town was finally renamed in honor of Queen Mercedes of Orléans, the first consort of Alfonso XII, son of Isabela II.

When the town was partitioned from Cauayan on January 20, 1886, the priest Pedro Jiménez named it after the late queen.

Poverty incidence of Reina Mercedes Source: Philippine Statistics Authority[14][15][16][17][18][19][20][21] As a municipality in the Province of Isabela, government officials in the provincial level are voted by the electorates of the town.

Reina Mercedes, belonging to the second legislative district of the province of Isabela, currently represented by Hon.