Barangay San Guillermo

Barangay San Guillermo forms part of San Nicolas, a municipality in Ilocos Norte, and is classified as a small barangay.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay San Guillermo had a population of 1,678. This made it the 13th largest of 24 barangays in San Nicolas by population, placing it in the middle tier of the municipality. Residents of Barangay San Guillermo accounted for approximately 4.31% 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 Guillermo moving from 1,777 residents to 1,678 residents, an intercensal change of -5.6%. The trajectory indicates a contracting community. The Philippine Statistics Authority classifies Barangay San Guillermo as urban, reflecting the density and built-up character of the area.

San Nicolas is a municipality comprising 24 barangays, and serves as the governing unit directly responsible for local services in Barangay San Guillermo, 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 Guillermo ranks 74th 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.