Barangay Sinaoangan Sur

Situated in San Agustin, Isabela, Barangay Sinaoangan Sur is one of 23 barangays that make up the municipality within Cagayan Valley.

According to the 2020 Philippine census, Barangay Sinaoangan Sur had a population of 547. This made it the 17th largest of 23 barangays in San Agustin by population, placing it in the middle tier of the municipality. Residents of Barangay Sinaoangan Sur accounted for approximately 2.48% of the total population of San Agustin, which stood at 22,096 in the same census year.

Census comparisons between 2015 and 2020 show Barangay Sinaoangan Sur moving from 609 residents to 547 residents, an intercensal change of -10.2%. The trajectory indicates a contracting community. Barangay Sinaoangan Sur is officially classified as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

San Agustin is a municipality comprising 23 barangays, and serves as the governing unit directly responsible for local services in Barangay Sinaoangan 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 Sinaoangan Sur ranks 914th 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.

Like every Philippine barangay, Barangay Sinaoangan Sur is led by an elected Punong Barangay (barangay captain) supported by seven Sangguniang Barangay members (kagawads), an SK Chairperson, a Barangay Secretary, and a Barangay Treasurer. The next Barangay and Sangguniang Kabataan Elections (BSKE) are scheduled for Monday, November 2, 2026, with officials serving four-year terms under Republic Act No. 12232.