Barangay Casili Sur

Situated in Camalaniugan, Cagayan, Barangay Casili Sur is one of 28 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 Casili Sur had a population of 649. This made it the 19th largest of 28 barangays in Camalaniugan by population, placing it in the middle tier of the municipality. Residents of Barangay Casili Sur accounted for approximately 2.57% of the total population of Camalaniugan, which stood at 25,236 in the same census year.

Census comparisons between 2015 and 2020 show Barangay Casili Sur moving from 645 residents to 649 residents, an intercensal change of +0.6%. The trajectory indicates a slowly expanding community. The Philippine Statistics Authority classifies Barangay Casili Sur as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Camalaniugan is a municipality comprising 28 barangays, and serves as the governing unit directly responsible for local services in Barangay Casili Sur, including public health, sanitation, peace and order, and civil registration. Within the wider province of Cagayan, which contains 820 barangays across its component cities and municipalities, Barangay Casili Sur ranks 674th by 2020 population. Cagayan is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

The barangay's legislative and executive affairs are handled by a Punong Barangay and the Sangguniang Barangay, elected nationwide during the Barangay and SK Elections. The next BSKE is scheduled for Monday, November 2, 2026, following the synchronized election schedule set by COMELEC Resolution No. 11191.