The task of subjugating Mindanao as well as that of tapping its resources was inherited by the Americans when Spain ceded the Philippines to the United States as provided in the Treaty of Paris on December 10, 1898. In relation to America's take-over, this paper will revolve on the following aspects: an estimate of the island's agricultural, industrial conditions, and commercial status when left by Spain; a narrative of the drama covering the establishment of American military rule over Mindanao; a presentation of the role played by the Americans in the development of Mindanao during their military rule over the island from 1899-1913; and an evaluation of the socio-economic and political transformation which Mindanao experienced within the specified period.