The city of Passi, in the interior of Iloilo province has one of the oldest parishes in the country, having been established by the Augustinians under the protection of San Guillermo:
The Augustinian Council held on August 29, 1590 accpeted “the convent of the tingues* de Passic as house of the Order.” – Angels in Stone, Pedro Galende, OSA, 1996
*Tingues referring to the Atis that were present in the area.
The first stone church was said to be large and artistic with an equally magnificent kumbento. However, it was destroyed by a fire caused by lightning. The reconstructed structures were again damaged by an earthquake in 1612:
…the church of San Guillermo (Passi), a very strong one made of stone, cracked on both sides; the roof, which had just been put up, crumbled down.
Another church was built but was again destroyed or damaged by an earthquake in 1787. Fray Apolinario Villanueva built or rebuilt (as per Galende) the structures between 1821 and 1837 while Fray Pedro Ceberio restored these in 1856. A typhoon blew away the roof in 1932. Galende also mentions that the orientation of the church was changed with the back now serving as the front but gave no date or year when this happened and why.