Ilagan, officially the City of Ilagan (; ; ), is a 1st class component city and capital of the province of Isabela, Philippines. According to the 2020 census, it has a population of 158,218 people making it the most populous city in the province. It holds the title as the most number of voters in the province with 98,565 electorates. Ilagan was a first class municipality before it became a city. The city is located on the central portion of the province of Isabela. It is bounded by nine municipalities: on the north by the municipalities of Divilacan, Tumauini, and Delfin Albano; on the west by the municipality of Quirino; on the east by the municipalities of Divilacan, Palanan, and the Pacific Ocean; and on the south by the municipalities of Gamu, Naguilian, Benito Soliven and San Mariano. Ilagan is approximately from Tuguegarao and from Metro Manila (linked by a national highway via Santa Fe, Nueva Vizcaya). With a total land area of , it is the largest city in the island of Luzon and the fourth largest city in land area in the Philippines, after Davao City, Puerto Princesa, and Zamboanga City. Etymology From an inversion of the Ibanag word nagali which means move or transfer in the English language, due to the relocation of the site of the capital from Naguilian Baculod to its present site in barangay San Vicente. The move was due to economy and security of the town. Another etymology, according to Fr. Julian Malumbres, Ilagan derived its name from the word laga, an Ibanag word for smallpox during the town's founding in 1686 where the disease was widespread. History Early history The town was then called by its native Gaddang settlers as Bolo during the pre-Spanish conquest era. It is one of the populous settlement during that period and site of the vast tobacco plantation in the region making it one of the most important economic areas in northern Luzon. Spanish colonial era Shortly after Juan de Salcedo conquered Northern Luzon in 1587, Gov. Rodrigo de Penalosa sent Capt. Pablo de Carreon to explore Cagayan Valley as well as to establish missions in towns. Among the Spanish missionaries who penetrated deeply into the region was P. Pedro Jimenez, who founded Ilagan. The town of Bolo was founded by the Dominicans in 1619 in honor of Saint Ferdinand of Castile. The old Bolo was situated