Agusan del Sur Province is a landlocked province of the Philippines located in the Caraga region in Mindanao. Its capital is Prosperidad and borders, from the north clockwise, Agusan del Norte, Surigao del Sur, Davao Oriental, Compostela Valley, Davao del Norte, Bukidnon, and Misamis Oriental.
Agusan del Sur is an elongated basin formation with mountain ranges in the eastern and western sides forming a valley, which occupies the central longitudinal section of the land. The Agusan River, which flows from Compostela Valley in the south towards Agusan del Norte in the north, runs almost in the middle of the valley and empties at Butuan Bay. The river has twelve tributaries: Wawa, Gibong and Simulao Rivers in the eastern side and Ojot, Pusilao, Kasilayan, Libang, Maasam, Adgawan, Cawayan, Umayam and Ihaon Rivers in the western side. These tributaries are fed by streams and creeks. The southern half of the province from the municipality of Veruela is an area filled with swamps and lakes, the biggest of which is Talacogon Lake.
The Agusan Valley was settled by a variety of cultural communities like the Manobos, Mamanwas and Higaonons. Archeological excavations in the lower Agusan valley plains have uncovered evidence of strong relationships between the region and the Southeast Asian states. A golden image of Javan-Indian design unearthed in the 1920s and molten jars uncovered in Prosperidad are indications that the region had commercial and cultural ties with the coast.
