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 7 September 1979. On 10 March 1997, the area was converted into a natural park with the signing of Proclamation No. 978 by President Fidel Ramos.