Ilocos Region, officially designated as Region I, is an administrative region in the Philippines occupying the northwestern section of Luzon. It covers 4 provinces, namely, Ilocos Norte, Ilocos Sur, La Union, and Pangasinan. The regional center is the City of San Fernando. Its population as determined by the 2020 Census was 5,301,139. This represented 8.52% of the overall population of the Luzon island group, or 4.86% of the entire population of the Philippines. Based on these figures, the population density is computed at 409 inhabitants per square kilometer or 1,059 inhabitants per square mile. Source: https://www.philatlas.com/luzon/r01.html