It is a 4th class municipality in the province of Pampanga, Philippines.
Baliwag was the traditional name of Sto. Tomas. It was christened after Sto. Tomas Apostol, whose festivity was solemnized on the 21st day of December 1792 and every year thereafter. The town was named Baliwag (Baliwag means tardy in Spanish) because the town?s people were always late in attending mass.
On September 15, 1792, Sto. Tomas as a new town was detached from its Matrix Minalin. The separation was historically verified. But on the 19th Day of December 1792, negotiation was carried out by the townspeople towards the political segregation of Sto. Tomas from its Matrix Minalin.
From the parish files on baptism, marriage and death, from January 1, 1830 to 1854, the town was written as Sto. Tomas de Baliwag and from 1855 to 1926, it was written Pueblo de Sto. Tomas.