When Mabini was separated from Bauan and because a town on January 1, 1918, it was composed of eleven barrios, one of which is Saguing. Saguing has several sitios, including sitio Sili.

Sili happened to get its name when a couple by the name of Kapitan Jacinto & Kapita Olyang left Bauan to settle in the place. This couple when they came brought with them seedlings of sili and distributed them to the people already living in the place. Whoever came to this place were surprised of the many sili plants they saw. Because of the abundance of this plant, people from nearby sitios began to call this place Sili.

With the coming of the years, population and income increased, then the people agreed to file a petition creating a sitio into a barrio. Some of the prominent people headed by Mr. Benjamin Villanueva filed a petition to the Municipal Council. It was unanimously approved and then it was passed to the Provincial Board. So, on June 30, 1972, Sili was created into a barrio was named Sto. Tomas. It was so named in honor of Mr. Tomas Villanueva, one of the founders of our town Mabini, and a well known resident of the place. He also became a Municipal Councilor in 1918.

Sto. Tomas is bounded on the north by Solo, on the east by P. Anahao and Estrella on the south by Pilahan and on the west by Solo. Its soil is favorably suited to rice, corn, camote, vegetables and coconuts. People are engaged in animal raising, weaving and embroidery for women and farming for man are the chief means of livelihood.

Formerly people brought their products to the commercial centers like Bauan and Batangas by carrying them on their shoulders or sleds pulled by cow. But now, roads have been constructed by the aid of the Provincial Governor.

With the untiring efforts of the barrio captain Mrs. Esperanza M. Villanueva and her councilmen, the barrio is gradually progressing.