In the early 19th Century Spanish Colonial era, the Municipality of Atimonan, Tayabas (now Quezon Province) had suffered frequent attacks of Pirates and outlaws. A man from this place named Mariano Aguilar thought of moving to a better place to live and dwell with his family. He asked a good friend and distant relative, Juan Salvador to go with him to find a nearby peaceful place to settle for good. Along with their immediate families, they walked through the forest southwest bound until they found a river. While traversing the riverside, they found a scenic body of water which was best described as ladder-like as the waters run over ladder-like steps. They initially named the place Hagdan-hagdan (ladder-like structure). As they moved further west, they found a huge plane where they later established the town proper. In this land, they built houses for their families and divided the land area between their family members, relatives and friends. The population grew bigger and before the end of the 19th century, this area was officially called Agdangan (from the word Hagdan-hagdan), a barrio of the nearby town Unisan, Tayabas.

As time went by, the two families realized that there was a pressing need to build a church, school building, marketplace, the government building and other facilities basic to the community. The Salvador family donated the site for the school buildings and the public cemetery while Aguilar family donated the lots for the Roman Catholic Church, the marketplace and the municipal building. The population bumped up as a result of influx of people from nearby municipalities and provinces adjacent to Tayabas. The Philippine National Railways established a permanent train station which also contributed to the migration of people to this place. The Aguilar and Salvador families, along with the civic organization led by Mr. Pedro Olase, again took proactive efforts to gain independence from Unisan. Their actions led to the foundation of the municipality of Agdangan, Province of Tayabas. The culmination of this endeavor happened on April 1, 1939 when President Manuel Quezon signed into a Law the creation of the Municipality of Agdangan, Tayabas. As of today, April 1 has been commemorated in honor of the town's foundation day and is commonly known as Agdangan Day.

President Quezon appointed Roque Aguilar as Mayor until the first election was held. The following year, Catalino Aguilar and Crispin Salvador were elected as Mayor and Vice Mayor respectively.

Source:(http://www.wowquezon.com/towns-and-cities/agdangan-quezon-facts-history-gov-officials-barangays/)