'Over hundreds of years, a remote area in the east side of the town of Lopez has been home to a tree that has become the name of a barangay inhabited by people who are getting rich. The four main people, Damaso Masaganda, Panteleon Villegas, Herminihildo Evangelista, and Adriano Villaplana, were searching for a place to farm and make a living. They found a long river with two rivers, a tree with auspicious leaves, and a tribe of ayta who live in small houses made of wood, rattan leaves, and anahaw. The elders in the tribe explained that the tree was called a Tan-AG tree, and many of the trees grow on the banks of the river. The people use the tree as a floor on their couches and refer to it as "matan-ag river."
The four people settled in the village and divided the area into two, TAN-AG ILAYA and TAN-AG IBABA. The area was divided by the pandan river, leading to the establishment of schools, a meeting house, and a day care center. The barangay chief, Pablito abrigo, continued to build a meeting house and day care center. However, he died in 1998 due to illness, and his brother Vito Abrigo took over as Punong Barangay. From 2002-2007, Alexander Arguelles was elected Barangay chief, enlarging and beautifying the Bahay Pulungan. From 2007-2013, the last captain, Alexander Arguelles, ran for office.
Captain Termer Kagawad Novelita Batbat served as barangay chief from 2007 to 2013, focusing on meeting house construction, tile flooring, and street lighting. He also built a foot bridge, a new school lot, and a covered court for parents and students. In 2016, she completed three terms as barangay chief in Tan-ag Ibaba.