[5] In the old days, the present site of San Agustin was a hinterland inhabited by headhunting Ilongots and some scattered bands of Aetas locally known as "Pogot".

From this town sailed forth a band of pioneers led by Juan Gumpal, Antonio Pintang, and Vicente Taguiam.

Not long after the scattered settlements grew into sitios and one of them was Lakay-lakay (named after the creek) on the western side of the Cagayan River.

[7] San Agustin is the home of the Nuang Festival the annual celebration in honor of the sturdy carabao and in recognition of the highly successful Carabao Upgrading Program of the local government, through the Office of the Municipal Agriculturist and its cooperating agencies and stakeholders.

Poverty Incidence of San Agustin 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.

San Agustin, belonging to the fourth legislative district of the province of Isabela, currently represented by Hon.