The exception is Palanan, which was established in 1625 by Spanish forces who arrived by ship from the Pacific coastal town of Baler in Tayabas province (now part of Aurora).

[15][16][17] The province was placed under the jurisdiction of a governor (Lieutenant Colonel of Cavalry Francisco Contreras y Urtasun) with Ilagan as the capital, where it remains up to present.

They were later moved to the uplands or variably assimilated by the Austronesians, from whom the Ibanags, Itawes, Yogads, Gaddangs, Irayas, Malawegs, and Paranans descended - who actually came from one ethnicity.

Various other peoples, mainly the Ilocanos, Pangasinenses, Kapampangans and Tagalogs, as well as Visayans, Moros, Ivatans, and even foreigners like the Chinese, Indians, Arabs, Spaniards and others were further infused to the native Cagayanes to become the modern Cagayano, and Isabeleño in the exact province, that we know today.

The dynasty was started by the patriarch of the family, Faustino N. Dy Sr., who served as the mayor of Cauayan from 1965 to 1969 and sat as provincial governor for 22 years (1969–1992), surviving the initial attempts of President Ferdinand Marcos to remove him for being a member of the political opposition during the imposition of Martial Law in 1972 and winning reelection in 1988 after his removal by President Corazon Aquino after he had sided with Marcos in 1986.

Cojuangco and Carag purchased the two haciendas themselves, displacing tens of thousands of farmers who were supposed to get those lands back a hundred years after the Spanish acquired them.

In the Social Action Center's newsletter, the "Courier," researcher Sabino Padilla Jr. documented and exposed the ways by which Cojuangco, Carag, the provincial government, and the military harassed the farmers who were supposed to get the land.

[31] It was also during the dictatorship that Marcos began awarding logging concessions to his cronies in the areas of the Sierra Madre region, which heralded the beginning of widescale deforestation and other environmental problems that affect the province since then, despite Marcos creating the Palanan Wilderness Area in 1978 which was later expanded by President Fidel V. Ramos to become the Northern Sierra Madre Natural Park in 1997.

The construction was protested by the Ifugao people due to the flooding of their ancestral lands,[33] but the dam was eventually completed in 1982, partially funded through a loan from the World Bank.

[34] After the People Power Revolution in 1986, many of the activists who had joined the underground movement decided to "surface," as the new administration of Corazon Aquino released political prisoners and initiated peace talks.

It was only in the 2004 elections that the family's control of the gubernatorial seat ended when Grace Padaca, a former journalist, won over Faustino Dy Jr. She was the first woman to serve as the governor of the province.

However, in September 1999 through court ruling which granted the petition to declare Republic Act 8528 unconstitutional, hence, the status of Santiago was reverted back to independent-component city, due to lack of plebiscite.

[53] As a result of the catastrophe, the National Irrigation Administration (NIA) indicated that it would review its protocols regarding the release of water in Magat Dam and improve its watershed.

[54] Isabela comprises an aggregate land area of 12,414.93 square kilometres (4,793.43 sq mi),[55] representing almost 40 percent of the regional territory.

It is home to one of the world's largest remaining low-altitude rainforests, with numerous unknown endemic species of flora and fauna and biological diversity in the protected area known as the Northern Sierra Madre Natural Park.

Mount Dos Cuernos peak has an elevation of 1,785 metres (5,856 ft) located in San Pablo near the border with Maconacon.

Other notable peaks in the Northern Sierra Madre Natural Park is Mount Cresta in Divilacan with an elevation of 1,672 metres (5,486 ft).

Languages not native in Isabela are also spoken there such as Maranao, Maguindanaon, Tausug, Pangasinan, Kapampangan, Cebuano and Hiligaynon to varying degrees by their respective ethnic communities within the province.

[98][99] With the presence of the Isabela State University, joint ventures and other foreign assisted projects and the Magat Dam contribute to the high productivity in agriculture.

[109][110] There are 238 marine fish species that were identified by the Bureau of Fisheries and Aquatic Resources in Isabela's coastal seaboard municipalities of Maconacon, Divilacan, Palanan, and Dinapigue.

[113][114] Solar and biomass power plants in the city of Cauayan and in the town of Alicia have started operating in 2015 to supplement the region's high energy demand.

The P7-billion worth 100 MW Solar PV project in the city of Ilagan is designed to reduce the current shortage of electricity that causes regular blackouts that results to industry closures as well as inconvenience to the consumers.

Public utility vans and small-time bus operators ply daily trips from Tuguegarao in Cagayan to Santiago City vice versa, while jeepneys and tricycles are commonly used as the basic mode of transportation within the province's jurisdiction.

The project's authorized budget contract, worth P1.5 billion, will traverse across the foothills of the Northern Sierra Madre mountain ranges, which cover 359,486 hectares.

[121][122] The secluded coastal settlements of Divilacan, Palanan, and Maconacon are frequently accessible only by boat or plane, making them difficult to reach at times of emergencies and calamities.

There are no highways connecting Ilagan's capital city to the coastal districts, denying locals access to basic commodities and social services such as health care.

Once completed, the route is projected to bolster coastal economies, citing Divilacan's 119-hectare beach and freshwater areas that have attracted tourists.

Additionally, the Agta and Dumagat communities in the vicinity have signed a memorandum of understanding with the provincial administration expressing their support for the road project.

New hotels and resorts have opened, mostly in the cities of Ilagan, Cauayan and Santiago, and the towns of Tumauini, Gamu, Roxas, Alicia, Burgos, Ramon, San Mariano and Cordon.

Top tourist attractions are the centuries-old churches; Magat Dam Tourism Complex, which houses Southeast Asia's biggest dam; Santa Victoria Caves, Pinzal Falls and Ilagan Sanctuary at Fuyot National Park; the white sand beaches in the coastal municipalities of Maconacon, Divilacan, Palanan, Dinapigue and islands of coastal Isabela; the world's biggest wooden lounge chair or butaka in Ilagan City; and various festivals and fiestas, including the Bambanti Festival annually celebrated every February, and the commemoration of the birth of the province during Isabela Day every May.