Barangay Naguilian Sur

Barangay Naguilian Sur forms part of City of Ilagan, a city in Isabela, and is classified as a small barangay.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Naguilian Sur had a population of 1,304. This made it the 47th largest of 91 barangays in City of Ilagan by population, placing it in the middle tier of the city. Residents of Barangay Naguilian Sur accounted for approximately 0.82% of the total population of City of Ilagan, which stood at 158,218 in the same census year.

Between the 2015 and 2020 censuses, the population of Barangay Naguilian Sur changed from 1,231 to 1,304, a shift of +5.9% over the five-year period. This places the barangay among those with growing populations in City of Ilagan. The Philippine Statistics Authority classifies Barangay Naguilian Sur as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

City of Ilagan is a city comprising 91 barangays, and serves as the governing unit directly responsible for local services in Barangay Naguilian Sur, including public health, sanitation, peace and order, and civil registration. Within the wider province of Isabela, which contains 1,055 barangays across its component cities and municipalities, Barangay Naguilian Sur ranks 497th by 2020 population. Isabela is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

Barangay Naguilian Sur is governed by an elected Sangguniang Barangay composed of a Punong Barangay and seven kagawads, with the Sangguniang Kabataan representing the youth. The next BSKE, set for Monday, November 2, 2026, will elect officials to four-year terms as provided under Republic Act No. 12232.