The Deep South is a cultural and geographic subregion in the Southern United States. The term was first used to describe the states most dependent on plantations and chattel slavery during the early period of United States history. The region suffered economic ruin after the American Civil War and was a major site of caste tension during and after the Reconstruction era. State governments enshrined white supremacy as a guiding principle and worked to deny political rights and economic opportunities to black citizens, partly through Jim Crow laws. The Civil Rights Movement ushered in a new era, sometimes referred to as the New South. Before 1945, the Deep South was often referred to as the Cotton States, since cotton was the primary cash crop.