The British built Fort King George as a step toward settling the Altamaha River region. The British needed to control the river systems in order to control economic activities and commerce in the Southeast, especially that pertaining to the fur trade. The Altamaha River is one of the largest and far-reaching rivers in the region, and it allowed passage throughout the territory, especially to the powerful tribes of the Creek/Muskogee found west of the river system. Fort King George was part of a plan by the British to control the Altamaha and to secure economic imperial superiority in the Southeast. The Spanish were the first to arrive in the Southeast, first with explorers, then with the settlement of St. Augustine in present-day Florida in 1565. They started creating a mission system, converting the Native American tribes and using them as workers for agricultural production. The city became a base so that the Spanish could protect their treasure ships carrying gold and silver from the South. They used missions to expand the Catholic faith to the numerous tribes found in the Southeast. The converted Native Americans were incorporated into the Spanish system of "repartimiento". They used an indigenous labor force capable of growing surplus grains for needy colonists in the Spanish-American Empire. By the mid-17th century, dozens of Spanish missions controlled the southeastern coastline with thousands of Native Americans drawn into and around them. This system centered on missions accompanied with troops occupying presidios. They created four mission provinces: Tumucua (interior northern Florida), Apalachee (northwestern Florida), Guale (Georgia coast north of the Altamaha River), and Mocama (from the Altamaha River south to the St. Johns River). The name Guale was possibly derived from a Native American chief of that name who was visited by Pedro Menéndez on St. Catherines Island in 1566. In that year, Menéndez established troops on that island. Santa Catalina de Guale would later become one of the largest and most productive missions by the mid-17th century. Another successful mission was Santo Domingo de Talaje. Established sometime in the early 17th century, this mission was located on a large bluff up the north branch of the Altamaha River. Native Americans had inhabited the bluff for thousands of years. The English later used this site as the location for Fort King George in the 1720s. Guale was threatened by the settlement of English Carolina immediately to the north, where Charlestown was established in 1670.