The Cagayan River, also known as the Río Grande de Cagayán, is the longest river and the largest river by discharge volume of water in the Philippines. It has a total length of approximately 505 kilometres (314 mi) and a drainage basin covering 27,753 square kilometres (10,715 sq mi). It is located in the Cagayan Valley region in northeastern part of Luzon Island and traverses the provinces of Nueva Vizcaya, Quirino, Isabela and Cagayan.
Cagayan Valley, designated as Region II, is an administrative region in the Philippines. Located in the northeastern section of Luzon, it is composed of five Philippine provinces: Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. The region hosts four chartered cities: Cauayan, Ilagan, Santiago, and Tuguegarao.
Isabela, officially the Province of Isabela, is the second largest province in the Philippines in land area located in the Cagayan Valley. Its capital and the largest local government unit is the city of Ilagan. It is bordered by the provinces of Cagayan to the north, Kalinga to the northwest, Mountain Province to the central-west, Ifugao and Nueva Vizcaya to the southwest, Quirino, Aurora and the independent city of Santiago to the south, and the Philippine Sea to the east.
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 and the second most-populous in Cagayan Valley after Tuguegarao. As of 2022, it also had the most number of voters in the province with 101,050 electorates.
Palanan, officially the Municipality of Palanan, is a 1st class municipality in the province of Isabela, Philippines. It also served as the final capital of the First Philippine Republic from 1900 until the capture of President Emilio Aguinaldo by the Americans during the Philippine-American War in 1901. According to the 2020 census, it has a population of 17,684 people.
Santiago, officially the City of Santiago, is a 1st class independent component city in the Cagayan Valley region of the Philippines. According to the 2020 census, it has a population of 148,580 people.
Alicia, officially the Municipality of Alicia, is a 1st class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 73,874 people.
Divilacan, officially the Municipality of Divilacan, is a 2nd class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 5,827 people.
Echague, officially the Municipality of Echague, is a 1st class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 88,410 people. The town is known for the indigenous and endangered Yogad language, which is spoken and conserved by its locals.
Gamu, officially the Municipality of Gamu, is a 4th class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 30,655 people.
Mallig, officially the Municipality of Mallig, is a landlocked 4th class municipality in the province of Isabela, Philippines. The municipality has a land area of 133.40 square kilometers or 51.51 square miles which constitutes 1.07% of Isabela's total area. Its population as determined by the 2020 Census was 32,208.
San Mariano, officially the Municipality of San Mariano; Ilocano: Ili ti San Mariano; Tagalog: Bayan ng San Mariano), is a 1st class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 60,124 people.
Tumauini, officially the Municipality of Tumauini, is a 1st class municipality in the province of Isabela, Philippines. According to the 2020 census, it has a population of 70,743 people.
The Pinacanauan River, also known as the Pinacanauan de Tuguegarao, is one of the rivers in the Philippines, and is a tributary of the Cagayan River. With a length of 46 kilometres (29 mi), the river originates in the Sierra Madre and passes through the Peñablanca Protected Landscape and Seascape, with large karst formations, underground chambers, and rare wild flora, before entering the Cagayan River in Tuguegarao, Cagayan. The Pinacanauan is considered one of the most picturesque attractions in Cagayan.
The Gaddang are an indigenous peoples and a linguistically identified ethnic group residing for centuries in the watershed of the Cagayan River in Northern Luzon, Philippines. Gaddang speakers were recently reported to number as many as 30,000, a number that does not include another 6,000 related Ga'dang speakers or other small linguistic-groups whose vocabularies are more than 75% identical.
The Peñablanca Protected Landscape and Seascape is a protected area and national park in Peñablanca, Cagayan. It is on the border with Isabela province, contiguous with the Northern Sierra Madre Natural Park. The protected area, best known as the location of Callao Cave, covers the largest block of forest under conservation in the province. It covers 118,781.582 hectares of the northern Sierra Madre mountain range and its adjacent Pacific coast.
The Northern Sierra Madre Natural Park is the largest protected area of the Philippines covering the northern range of the Sierra Madre mountains of eastern Luzon. The park is located in the eastern part of the province of Isabela in Cagayan Valley containing a total of 359,486 hectares. It was first declared a wilderness reserve encompassing an area within a 45 kilometres (28 mi) radius of Palanan Point known as the Palanan Wilderness Area through Letter of Instructions No. 917-A signed by President Ferdinand Marcos on September 7, 1979. On March 10, 1997, the area was converted into a natural park with the signing of Proclamation No. 978 by President Fidel Ramos.
The Sierra Madre is the longest mountain range in the Philippines. Spanning over 540 kilometers (340 mi), it runs from the province of Cagayan down to the province of Quezon, forming a north–south direction on the eastern portion of Luzon, the largest island of the archipelago. It is bordered by the Pacific Ocean to the east, Cagayan Valley to the northwest, Central Luzon to the midwest, and Calabarzon to the southwest. Some communities east of the mountain range, along the coast, are less developed and so remote that they could only be accessed by taking a plane or a boat.
The Quirino Protected Landscape is a protected area in the Philippine island of Luzon that covers a large portion of the province of Quirino. It was established in 2004 to preserve the watershed area containing the headwaters of the Cagayan River, also known as the Rio Grande de Cagayan, which supports major irrigation systems in the entire Cagayan Valley region. From an initial area of 206,875.41 hectares, the protected area now forms a total aggregate area of 175,943.62 hectares divided into three parcels after a 2005 amendment opened up a few areas to mining. It is a key biodiversity area of the Sierra Madre Biodiversity Corridor.
The Ilagan–Divilacan Road is one of the infrastructural components being considered for building that would connect the city of Ilagan with the coastal town of Divilacan, both located in the province of Isabela. The road stretches approximately 82 kilometers through the Sierra Madre mountain range, giving better access to the remote towns in the province of Isabela, eastern coast. The road will be important for enhancing transportation and economic opportunities in the area and with regard to the access of goods and services to otherwise isolated areas.
