Glan Hinterlands were sparsely populated by native highlanders, particularly, B'laans, Manobos, Bagobos, Tagacaolos and Tagabelles. The coast was occupied by Sangils. It was during the coming of the early Chinese and Arab traders that Sarangani shore became a trading port. The coast was frequented by sea pirates who brought along looted treasures. In the late 14th century, Muslim missionaries arrived in the area and introduced Islam. The Sangils were the first converts to Islam Faith in Sarangani This explains the claim of historians placing this coastline inhabitants of the bay in the list of thirteen tribes of Muslim Filipinos.
Hispanic
The King of Spain sent four expeditions to the Philippines after the death of Magellan. The first three expeditions led by Garcia Jofre de Loisa in 1525, Sebastian Cabot in 1526, Alvaro de Saavedra in 1527 had all met their dismal end. The fourth expedition headed by Ruy Lopez de Villalobos reached Mindanao and drifted towards Sarangani Bay. "It reached the Island on February 2, 1543 and named the place Mindanao: Caesarea Caroli in honor of King Charles I (Emperor Charles V). By sailing along Sarangani Bay, in search of provisions, Villalobos fortuitously baptized the whole archipelago: Islas Filipinas: Philippine Islands, in honor of Prince Philip of Asturias, who became King Philip II." (History of the Philippines: A Focus on the Christianization of Bohol 1521-1991: Fr.Josemaria S. Luengo, PhD, pp 35-36) This account strengthens Sarangani's own share of that glorious past - an untold part of the Philippine History which Glan can now lay claim as it positioned in the mouth of the bay
American Colonial Period
The Pioneering Spirit Gov. Gen. Francis Burton Harrison appointed Don Tranquilino Ruiz of Alegria, Cebu as Superintendent of Agricultural Colony No. 9 in 1914. Colony No. 9 was one of the Agricultural Colonies established in Mindanao (then Moro Province) thru Colonization Law of Don Sergio Osmena, Sr., then Speaker of the House of Representatives.The first wave of 16 Cebuano settlers came to Glan on October 18, 1914. The second batch arrived on March 10, 1915.They opened and tilled the fertile soil of Glan. Vast tracks of land were planted to corn and coconut. And thus, "this interminable coconut fronds that line the vista of Glan is a story unto itself. It is a story of how group of men and women of true grit and fortitude overcame a future fraught with peril and uncertainties ..."The perfect townsite is credited to the Chief Surveyor James C. Cook who surveyed the area and made the town plan of beautiful symmetry in 1917.