Barangay 1 Castillo (Pob.)

Barangay 1 Castillo (Pob.) forms part of Pagbilao, a municipality in Quezon, and is classified as a small barangay.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay 1 Castillo (Pob.) had a population of 1,603. This made it the 15th largest of 27 barangays in Pagbilao by population, placing it in the middle tier of the municipality. Residents of Barangay 1 Castillo (Pob.) accounted for approximately 2.04% of the total population of Pagbilao, which stood at 78,700 in the same census year.

The barangay recorded 1,892 residents in the 2015 intercensal count and 1,603 residents in the 2020 Census — a net change of -15.3%, consistent with a contracting settlement. The Philippine Statistics Authority classifies Barangay 1 Castillo (Pob.) as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Pagbilao is a municipality comprising 27 barangays, and serves as the governing unit directly responsible for local services in Barangay 1 Castillo (Pob.), including public health, sanitation, peace and order, and civil registration. Within the wider province of Quezon, which contains 1,242 barangays across its component cities and municipalities, Barangay 1 Castillo (Pob.) ranks 405th by 2020 population. Quezon is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

Barangay 1 Castillo (Pob.) 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.