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.

However, an expedition in September and October 2012 to Mount Guiwan (Nueva Vizcaya) preliminarily measured an altitude of 6,283 feet (1,915 m) on the summit.

Sierra Madre is home to Indigenous Dumagat-Remontado communities[6] who have ancestral domain claims covering parts of the mountain range.

[9][10] The Sierra Madre mountain range is rich in genetic, species, and habitat diversity,[11] supplying food, water, and shelter to millions of people.

[12] Northern Sierra Madre Natural Park, the largest protected area in Sierra Madre range, is home to endemic dipterocarp trees belonging to the Hopea and Shorea genera, orchids such as Dendrobium aclinia, the leguminous tree, Milletia longipes and a member of the citrus family, Swinglea glutinosa as well.

[16] Pterocarpus indicus ("Narra"), the national tree of the Philippines, Agathis dammara ("Almaciga"), and Diospyros blancoi ("Kamagong") can be found on the Sierra Madre range.

[17] A gold and copper mine in the municipality of Kasibu, Nueva Vizcaya, has been operated by the OceanaGold Corporation based in Australia.

[18] Oceana continues to assert a right to operate despite expiration of its permit, and opposition by organized local residents, the Catholic Church, and worldwide environmental groups.

[20] This project replaced the Kaliwa Low Dam that did not materialize and under the new administration, Rodrigo Duterte approved the Chinese-funded proposal.

[23] The Mabuwaya Foundation is a non-governmental organization that aims to protect and conserve the Philippine crocodiles and other endemic threatened species.

[24][25] On June 19, 2012, in light of the onslaught of Tropical Storm Ondoy on September 26, 2009, Philippine president Benigno Aquino III signed Proclamation No.