The Santee River is a river in South Carolina in the United States, approximately 143 mi (230 km long). The Santee and its tributaries provide the principal drainage and navigation for the central coastal plain of South Carolina, emptying into the Atlantic Ocean approximately 440 mi (710 km) from its farthest headwater on the Catawba River in North Carolina, Much of upper river is impounded as the expansive horn-shaped Lake Marion reservoir, formed by the 8 mi (12.9 km) long Santee Dam, built during the 1930s as a WPA project to provide a major source of hydroelectric power for the state.
The Santee is formed in central South Carolina approximately 25 mi (40 km) southeast of Columbia by the confluence of the Wateree and Congaree rivers. It flows southeast for approximately 5 mi (8 km) before entering the northwest corner of Lake Marion, which stretches in a long wide arc to the southeast for approximately 30 mi (48 km) to Santee Dam. A navigable diversion canal first built in the 1790s at the southern tip of the lake connects to Lake Moultrie, a reservoir on the nearby Cooper River. The modern canal is operated by Santee Cooper as part of the larger hydroelectric project on both rivers.
Downstream from the reservoir it flows east, then southeast, forming the northeast boundary of Francis Marion National Forest. Approximately 10 mi (16 km) from its mouth it bifurcates into two channels, called the North Santee and South Santee, that flow parallel and separated by approximately 2 mi (3.2 km), creating Cedar Island. The two channels reach the ocean at Santee Point, approximately 15 mi (24 km) south of Georgetown.
The river was named by early settlers after the Santee tribe, which inhabited areas on the middle part of the river. The first European contact was by the Spanish, who sailed up the river in the 1660s. After suffering a defeat by the British in 1715-1716, the Santee were relocated, many to the West Indies as slaves, opening up the river for British settlement as part of the Carolina Colony.
In the late 18th century the upper river was the site of the homestead of Francis Marion, a patriot of the American Revolutionary War. The original site of his homestead is now located under Lake Marion, which is named in his honor.
Construction of the 22 mi (36 km) long Santee Canal linking the river to the Cooper was begun in 1793 and finished in 1800. It allowed direct water transportation between the Upcountry of central South Carolina to Charleston, on the mouth of the Cooper. The canal operated for 50 years before becoming obsolete by the introduction of railroads.