The province borders Cagayan to the north and east, Abra and Ilocos Norte to the west, and Kalinga to the south.

Prior to 1995, Kalinga and Apayao comprised a single province named Kalinga-Apayao, which was partitioned to better service the needs of individual ethnic groups.

[4] Although Apayao which was then part of Cagayan,[5] was among the earliest areas penetrated by the Spaniards in the Cordilleras, the region, inhabited by the Isneg tribe, remained largely outside Spanish control until late in the 19th century.

The comandancias, however, failed to bring total control and the Spanish government only maintained a loose hold over the area.

[4] While the Isneg clashed with the Philippine Constabulary in the early years, the families attempted to escape the area and go into the mountains of Ilocos Norte and Abra.

[4] In 1942, Japanese Imperial forces entered Apayao, starting a three-year occupation of the province during the Second World War.

[further explanation needed] Local Filipino troops and the military forces of the 11th and 66th Infantry Regiment, Philippine Commonwealth Army, USAFIP-NL, supported by the Cordilleran guerrillas, drove out the Japanese in 1945.

[further explanation needed] During the Second World War, Kabugao was occupied for a year by the Japanese; an Isneg guerilla force was organized under a United States Army captain who had escaped the Fall of Bataan.

Little fighting occurred in the sub-province, but a number of Isneg fought with the American and Filipino forces in the Cagayan Valley and in the neighboring areas.

[15] During his bid to be the first Philippine president to be re-elected for a second term, Ferdinand Marcos launched an unprecedented number of foreign debt-funded public works projects.

[27] Apayao was deeply affected by events that took place in its sister sub-province of Kalinga, as well as the neighboring provinces of Abra and Mountain Province (Bontoc, including the struggle against the Chico Dam Project, the struggle against the encroachment on indigenous lands of logging company Cellophil Resources Corporation owned by Marcos crony Herminio Disini, and the rise of multiple armed Cordilleran autonomy movements.

[26][28] After Marcos was finally deposed by the civilian-led 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.

[30] However, anti-left sentiment in Aquino's new cabinet, which included figures who had sided with the Reform the Armed Forces Movement, made the peace process difficult, and negotiations eventually collapsed, and the insurgency in Kalinga-Apayao persisted.

[34] Either way, this set the stage for negotiations which would eventually lead to the creation of the Cordillera Administrative Region, and Apayao as an independent province within it.

The province covers an area of 4,413.35 square kilometres (1,704.00 sq mi)[40] forming the northern tip of the Cordillera Administrative Region, and is bounded on the north and east by Cagayan, west by Ilocos Norte, southwest by Abra and south by Kalinga.

[44] The province is home to critically endangered rufous hornbills, lawaan or dipterocarp trees, Raflesia flowers, and the white-winged flying fox.

[45] On March 22, 2013, scientists discovered the stronghold of critically endangered Philippine eagles, the country's national bird, in Luzon island within the vicinity of the Calanasan Lowland Forest.

The province, which possesses more than 286,000 hectares of virgin forests, also noted that they have sent four of their personnel to train in the United States under the US Foreign Service to hasten the declaration of the site.

Fruits produced include lanzones, citrus, bananas and pineapples, durian, santol, rambutan, coconut and mangosteen.

Other additional investment includes manufacturing, food processing, furniture, crafts and house wares making.

[73][76] In 1913, a band of Isneg attacked Tauit, as they were infuriated by the large number of Ilocano settling in the territory under the protection of the local government.