Sto. Tomas was one time a big barrio of five sitios , namely: Cabuloan , Camanggaan , Camindoroan , Calanutian and Centro Sto. Tomas and were inhabited by settlers from the Ilocos provinces and La Union . prominent among the migrant and adventurous Ilocanos were the Mariano , Rodrigo , Agpasa, Sermonia, Hermano, Aquino and others who established their homes beside the Agno River with farming and finishing as their primary source of livelihoods . It was bustling  community along the river and was named by the faithful and religious inhabitants as Barrio Sto, Tomas became their patron saint.

            In the 60’s the PACD creation of barangays to intensify countryside development divided the big barrio into five separate barangay with Sitio Centro becoming Sto. Tomas Centro. Sto Tomas Centro is bounded on the north by Brgy. Camindoroan on the south by Brgy. Camanggaan, and Cabuloan , on the east by Brgy . Malilion , and on the west by the Agno River.

             Sto. Tomas Centro is the most populated barangay among the five barangay which composed the Sto. Tomas District and often called as the 5C barangays. As the name implied, Sto. Tomas Centro is the center of the whole district in which the elementary and high schools are located. Presently it is composed of three sitios, namely: Sitio Aquino, Sitio Laud and Sitio Parking. Farming is the primary  source of living of the people with palay, corn, tobacco and vegetables as their main crops . other sources of income are pottery making, finishing , bamboo craft and livestock raising .

            Presently , Sto.Tomas high School , under the tutelage of principal Mrs. Virginia A. Arciosa , is reaping success and recognition in athletics particular in the archery event. Their Archery teams, both in men and women division are Ilocos regional athletic meet champions ( Gold medaling ) randy Collado and Mary Ann Castro were likewise finalist in their respective events in the 1997 and 1998 palarong pambansa.