The foundation of Calilaya, the capital of the old province of Calilaya, by Friar de Plasencia and Friar de Oropesa started in 1578. The first church was made of bamboo and nipa. In 1589, Friar Pedro Bautista obtained the permission to rebuild it with wood. Friar Alonso Bañon administered Calilaya after 1595. Friar Jode de la Concepcion was Guardian of the convent in 1597. Friar Pedro de Alcazar administered the pueblo in 6100 and 601. Friar Juan Manso was the religious minister in 1602. Friar Diego de la Magdalena, a member of the 6th Mission that arrived in the Philippines in 1594, also administered Calilaya. In 1605, Calilaya was ravaged by the Moros. Of the 9,000 residents, barely 1,000 survived the attack. The survivors took refuge near the Pasabango River, where the missionaries, among whom was Friar Pedro de san Buenaventura, built a church, a convent and school buildings with bamboo and nipa. Friar Juan de Merida administered Pasabango in 1609. In 1913, because of the crocodiles, the people relocated to the sitio of Cabuyao, where Friar de Merida built a church and a convent with wood and school buildings with bamboo and nipa. The people lived peacefully in Cabuyao until 1635, when the Moro attacked again. Some 800 survivors took refuge in the sitios of Atimonan and Minanucan (now barrion Talaba in Atimonan). Hence, for many years the town of Calilaya was totally abandoned. From 1620 onwards, a certain Gregorio Vicente united various families from Cabuyao with wandering descendants of those who had lived in Calilaya and Pasabango, and he and all these people fixed there residence in the site of old Calilaya---the delta east of the Calilaya River---without recognizing any civil or religious authority. They lived there until 1637 when the Government saw the need to burn the town. Finally in 1874 or 1875, the town was established in the outskirts of the
old Calilaya. During its early years, Unisan was administered by Fr. Marcos Tolentino, a secular priest, who In 1945, during the World War II, the church was partially destroyed; it was reconstructed by the Philippine Historical Commission in 1966.