By 1900, although industrialization (mainly textile manufacturing) was increasing, South Carolina was still mainly dependent on agriculture. During the early years of the century the state underwent a general economic decline. Rice had ceased to be a major crop and cotton suffered from the effects of soil depletion and the boll weevil. Thereafter, although tobacco emerged as a profitable crop, agriculture decreased in economic importance.

After World War I there was a large black migration to northern states, and by 1930 whites outnumbered blacks in the state for the first time in more than a century. World War II brought increased prosperity as textiles and food products were in great demand. There was rapid industrialization in the postwar period, as many new industries were attracted by the state's abundant raw materials and low-cost labor.

During the years following the war, South Carolina was the scene of much racial discord as blacks began to demand civil rights. In the Presidential election of 1948 the state cast its electoral votes for its governor, J. Strom Thurmond, who ran on a segregationist platform. When the U.S. Supreme Court ruled in 1954 that public schools must be desegregated, South Carolina was among the states that refused at first to comply. The state began integrating its schools in 1963. In 1970 three black representatives were elected to the previously all-white state legislature.

In the early 1970's a program was initiated by the state to improve all levels of public education. During the late 1970's all municipalities and most counties were reorganized as required by a series of laws, enacted by the legislature in 1975, aimed at modernizing local government. The economy suffered during the national recession of the early 1980's but had rebounded by the late 1980's. In 1989 Hurricane Hugo caused widespread damage, especially in the Charleston area.

In 2003, Congaree Swamp National Monument was changed to Congaree National Park, making it the first national park in the state.