Tarangnan is politically subdivided into 41 barangays.
On the earlier part of the 18th century, Tarangnan was the first settlement of the Jesuits missionaries in the island of Samar. Even before the explusion of the Jesuits, Moro raids have already begun as early as 1750. Samar though was not their major target because of its poverty. Most of its coastal settlements were often attack by Moros as they return to their bases in Mindanao and Sulu after raiding affluent places in Luzon, Bicol and West Visayas. Hence, for greater safety, the people settling in Tinago, now Tarangnan, moved to an interior site called Dapdap.
In the second half of the nineteenth century, the island of Samar experienced a commercial boom especially in abaca with imports and exports of said products. Moro raids in the island have declined due to the presence of Spaniards. As the Spaniards settled in Samar, They saw the need of all w eather seaports and easy communications for their commercial activities and political administration. This development paved the way for the convergence of the inhabitants into the old town site of Tarangnan where transport was relatively accessible. The settlement of Tarangnan indeed, was growing at a much faster pace than the pueblo of Dapdap. Taking into consideration of the island’s commercial boom with prospect of Tarangnan as a trading center and its religious vigilance over Dapdap, Gov. Enrique Chacon on June 21, 1881 wrote his superiors recommending the transfer of the Poblacion suggesting that the Poblacion be transferred from Dapdap to Tarangnan due to the former’s poor accessibility, unavailability of land area for expansion and its unsanitary environment. On April 1, 1884, Tarangnan was declared as one of the municipalities of the Province of Samar by means of Royal Decree by the King of Spain, King Alfonso I The Municipality of Tarangnan has forty-one (41) duly constituted barangays with a total land area of approximately 10,417.1435 hectares, having a population of 18,791 based on the 1995 NSO data. The Municipality is geographically situated in the west portion of the island of Samar, bounded on the east by the municipality of Pagsanghan, in the south by the capital city of Catbalogan and on the west by the Samar Sea or Maqueda Bay. Tarangnan is accessible by either land or sea. The distance of the poblacion from the capital city of Catbalogan is about 36 km and 59.75 km away from Calbayog City. It can be reached through an 11-km road from the maharlika highway crossing Brgy. Balugo by a provincial road. A 5th class municipality belonging to the 1st Congressional District of the Samar province, Tarangnan has its own municipal hospital which was inaugurated in 1982. It is a 10-bed capacity which caters primary health services and augmented by Rural Health Unit extension workers. It has daycare centers which also cater the needs of pre-schoolers.
Tarangnan has been estimated some years back to have a low literacy rate, but with the opening of primary education in some barangays and expansion of the secondary education (Tarangnan National High School) in Brgy. Oeste, it dramatically rose-up to 89.95% as recorded in NSO 1995 survey. The Municipality’s energization/electrification program is being undertaken by Samar Electric Cooperative (SAMELCO I) based in Calbayog City. Presently, around 21 barangays or 52% of the total number of barangay are fully energized. Others without such facilities are using power-generator sets to provide electricity to its constituents. Water Supply is predomonantly on Level I and II, and its sources are believed to be potable. Coping along with the reforestation program of the government, the municipality has already started its reforestation activities and is still focusing to achieve its target of 30% reforested area by the year 2005 Aside from implementation of the Fishery Laws and PD 701, Fish Sanctuaries and Marine Reserve Area were installed along the shorelines of some island barangays along the Cambatutay Bay to complement the substantial measures in protecting the marine resources. Majority of these projects were initiated by the WESAMAR (an EU-GOP Funded project by the Department of Agriculture) together with the Community-Based Organizations.