Barangay Calamagui 1st

Classified as a mid-sized barangay, Barangay Calamagui 1st is one of the administrative divisions of City of Ilagan in Isabela, Cagayan Valley, Philippines.

According to the 2020 Census of Population and Housing conducted by the Philippine Statistics Authority, Barangay Calamagui 1st had a population of 3,918. This made it the 7th largest of 91 barangays in City of Ilagan by population, placing it among the most populous barangays of the city. Residents of Barangay Calamagui 1st accounted for approximately 2.48% of the total population of City of Ilagan, which stood at 158,218 in the same census year.

Between the 2015 and 2020 censuses, the population of Barangay Calamagui 1st changed from 3,619 to 3,918, a shift of +8.3% over the five-year period. This places the barangay among those with growing populations in City of Ilagan. The Philippine Statistics Authority classifies Barangay Calamagui 1st as urban, reflecting the density and built-up character of the area.

City of Ilagan is a city comprising 91 barangays, and serves as the governing unit directly responsible for local services in Barangay Calamagui 1st, 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 Calamagui 1st ranks 55th 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.

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.