Santiago is a fourth class municipality in the province of Ilocos Sur, Philippines. According to the 2015 census, it has a population of 18,759 people. Santiago Cove is dubbed as the "Boracay of Ilocos Sur" because of its white sands. Santiago is the headquarters of the Ilocos Sur Electric Cooperative (ISECO), which distributes electricity to the entire province. ^ Census of Population. "Region I ". Total Population by Province, City, Municipality and Barangay. PSA. Retrieved 20 June 2016.