Cagayan Valley (; ), is an administrative region in the Philippines, located in the northeastern section of Luzon Island. It is composed of five Philippine provinces: Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. The region hosts four chartered cities of Cauayan, Ilagan, Santiago, and Tuguegarao. Most of the land area is situated on the valley between the Cordilleras and the Sierra Madre mountain ranges. The eponymous Cagayan River, the country's largest and longest, runs through the region and flows from the Caraballo Mountains and ends at Aparri. Cagayan Valley is the second largest Philippine administrative region by land area. According to a literacy survey in 2013, 97.2% of Cagayan Valley's citizens (ages 10 to 64) are functionally literate, which is the highest out of the seventeen regions of the Philippines. History Archaeology indicates that Cagayan has been inhabited for half a million years, though no human remains of any such antiquity have yet appeared. The earliest inhabitants are the Agta, or Atta, food-gatherers who roam the forests without fixed abodes. A large tract of land has lately been returned to them. The bulk of the population are of Austronesian origin. For centuries before the coming of the Spanish, the inhabitants traded with Indians, Malays, Chinese, and Japanese. In the nineteenth century, the prosperity found in tobacco cultivation caused many Ilokano people to settle here. Tobacco is still a major factor in the economy of Cagayan, though a special economic zone and free port has been created to strengthen and diversify the provincial economy. During the Spanish era, Cagayan Valley had a larger territory than today. Then it included the territories of the above-mentioned provinces and the eastern parts of the Cordillera provinces of Apayao, Kalinga, Ifugao and Benguet, and the north part of Aurora. Historian and missionary Jose Burgues said, "The old Cagayan Valley comprises the province of Cagayan, Isabela and Nueva Vizcaya as well as the military Districts of Apayao, Itaves, Quiangan, Cayapa and Bintangan, plus the area of the Sierra Madre to the Pacific Ocean in the said trajectory." During World War II, at Balete Pass in Nueva Vizcaya, the retreating Japanese Imperial Army under General Tomoyuki Yamashita dug in and held on for three months against the American and Filipino forces who eventually drove them out; the pass is now called Dalton Pass in honor of General Dalton, USA, who was killed in the fighting. Geography Cagayan