Around the 1580s, the Franciscan Friars began the systematic process of Hispanization and Christianization called reduccion, a system that involves two major processes of socio-cultural transformation: urbanization and Christian instruction.

The Spanish missionaries observed that the natives tended to live near the field or on the hills where they planted crops in the mountains and forest where they hunted or beside the rivers or along the seacoasts, particularly in sheltered bays and protected channels between the many islands, where seafood abounded. The rivers and seas likewise provided them with means of escapes from enemies and avenues of travel and communication. Those who lived inland were, in most cases, into slash and burn type of agriculture. There was neither a town nor a city in the European style, let alone a central government that unified the natives.

Because the natives lived in scattered settlements far from each other, it was extremely difficult for the missionaries to catechize and administer the sacraments to them unless they came together to live in larger communities and build their own towns and churches.

Friar Juan de Plasencia took a leading role in resettling the dispersed natives into compact villages or poblaciones or, in other words, in reducing the small, scattered settlements into larger settlements as people of that time used to say. He urged the natives to concentrate into the plains, where they should be taught how to till the land. Furthermore, he took advantage of a royal decree granting aid to missionaries for the construction of churches in their mission areas. To accelerate the reduccion of the natives, he asked the Spanish monarch and the governor of Manila to compel them to live in towns.

Once the natives were resettled in suitable places they could be under the protection of the missionary, "who would teach them how to build and to furnish simple human habitations as well as agriculture and other elements of progress." The head settlement or cabecera, where the basic elements of Spanish urban life where found, constituted the poblacion or the capital of what would come later as the pueblo. Plasencia's project of forming "pueblos de indios" proved to be so successful that his methods were accepted by all missionary groups working in the Philippines.

In implementing the reduccion policy, the missionaries followed what Spanish law had already dictated on how to establish towns and cities. The poblacion had to follow on gridiron pattern, withrectangular street blocks and with streets "drawn a cordel y a regal (straight and at right angles to one another) at the center is the church, and within its perimeter was the cemetery. The people were to live literally and symbolically debajo de la campa, under the bell or within hearing distance of the bell. (Excerpts from Fr. Renato Pareja's book History of the Diocese, 2010)