Pedro de Santo Tomas, making it the oldest town in Isabela and existing before the province's creation.

It was then renamed to Cabagan, loosely interpreted as the place where people wear "ba-ag" or "G-strings" when the Spaniards arrived at the Philippine Islands.

[7] Mengal Baladdon and his troops, disturbed by Fray Pedro Jimenez's success in establishing Christian communities in the Irraya, devastated Cabagan in 1683, killing twelve people and forcing the locals to escape to the mountains.

Cabagan Viejo was then renamed to San Pablo, after its patron saint Paul the Apostle whose feast day is celebrated every January 15.

Poverty incidence of San Pablo Source: Philippine Statistics Authority[15][16][17][18][19][20][21][22] The Baka (Cow) Festival, inaugurated in 2004, is held annually on January 15.

According to accessible documents, the three Capitan Municipals of San Pablo served in the latter half of Spanish administration when Cabagan Viejo was re-established.

[7] San Pablo's municipal mayors during the Commonwealth period, Japanese occupation, and the Third Republic include[7] These were the municipal mayors during the Fifth Republic, under the 1987 constitution: San Pablo, belonging to the first legislative district of the province of Isabela, currently represented by Hon.