Barangay Quimalabasa Sur

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

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Quimalabasa Sur had a population of 392. This made it the 22nd largest of 23 barangays in San Agustin by population, placing it among the smaller barangays of the municipality. Residents of Barangay Quimalabasa Sur accounted for approximately 1.77% of the total population of San Agustin, which stood at 22,096 in the same census year.

The barangay recorded 509 residents in the 2015 intercensal count and 392 residents in the 2020 Census — a net change of -23.0%, consistent with a contracting settlement. The Philippine Statistics Authority classifies Barangay Quimalabasa Sur 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 Quimalabasa 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 Quimalabasa Sur ranks 994th 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 Quimalabasa 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.