The Santee River was dammed in the 1940s to supply hydroelectric power, as part of the rural electrification efforts initiated under President Franklin D. Roosevelt's New Deal during the Great Depression.

Hydroelectric facilities at Pinopolis Dam were designed to produce the lion's share of power under the original scheme: it generates about 128 megawatts.

In 1985, as part of a large-scale rediversion and redesign, the United States Army Corps of Engineers installed the St. Stephen Dam hydro facility to recapture lost generating capacity of another 84 megawatts.

Religious groups, fraternal organizations, and rowing teams come to Lake Marion each spring and summer due to its sheltered location, calm waters, and temperate climate.

Other wildlife at Lake Marion include deer, fox, squirrel, turtle, dove, wild turkey, alligator, and various species of duck, hawk, eagle, egret, and osprey.