Barangay San Marcos

Classified as a mid-sized barangay, Barangay San Marcos is one of the administrative divisions of San Nicolas in Ilocos Norte, Ilocos Region, Philippines.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay San Marcos had a population of 3,006. This made it the 1st largest of 24 barangays in San Nicolas by population, placing it among the most populous barangays of the municipality. Residents of Barangay San Marcos accounted for approximately 7.73% of the total population of San Nicolas, which stood at 38,895 in the same census year.

Census comparisons between 2015 and 2020 show Barangay San Marcos moving from 2,675 residents to 3,006 residents, an intercensal change of +12.4%. The trajectory indicates a growing community. The Philippine Statistics Authority classifies Barangay San Marcos as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

San Nicolas is a municipality comprising 24 barangays, and serves as the governing unit directly responsible for local services in Barangay San Marcos, including public health, sanitation, peace and order, and civil registration. Within the wider province of Ilocos Norte, which contains 559 barangays across its component cities and municipalities, Barangay San Marcos ranks 11th by 2020 population. Ilocos Norte 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.