The Bahamas were discovered by Europeans in 1492, when Columbus made his first landing in the West Indies on San Salvador, or Watlings Island. The Spaniards transported the aboriginal population of Lucayan Indians to Hispaniola and Cuba to work in mines, and within twentyfive years of Columbus's arrival the islands were depopulated. During the latter half of the seventeenth century the islands were colonized by English settlers, who brought along their slaves. By 1773 the population, which totaled approximately 4,000, had an equal number of Europeans and people of African origin. Between 1783 and 1785 many Loyalists who had been expelled from the American colonies immigrated to the islands with their slaves. These slaves, or their parents, had originally been transported to the New World from West Africa during the eighteenth century to work on cotton plantations. This influx to the Bahamas increased the number of Whites to approximately 3,000 and the number of slaves of African ancestry to approximately 6,000. Most of the slave plantations established by the Loyalists in the Bahamas were on the "Cotton Islands"—Cat Island, the Exumas, Long Island, Crooked Island, San Salvador, and Rum Cay. At first they were successful economic enterprises; after 1800, however, the production of cotton declined because the slash-and-burn technique used to prepare the fields for planting depleted the soil. Following the emancipation of slaves in the British Empire in 1838, some departing plantation owners gave their land to their former slaves, and many of these freed slaves adopted the names of their former owners in gratitude. At the time of Emancipation the English captured a number of Spanish ships transporting slaves taken in the Congo, the primary site of slave-trade activity after 1800, and brought their human cargo to special village settlements on New Providence and some of the other islands, including Long Island. The newly freed Congo slaves who went to the Exumas and Long Island intermarried with former slaves who were tilling the soil of the abandoned plantations. With the increased number of occupants on already depleted land, many were forced to migrate and Long Island and the Exumas experienced a decline in population after 1861. From the middle of the nineteenth century onward, Bahamians sought ways to bring prosperity to the islands. During the U.S. Civil War they engaged in blockade-running and gunrunning from New Providence to the southern states. Later attempts at large-scale export of agricultural products, such as pineapple and sisal, failed as more successful growers emerged elsewhere. Sponge gathering flourished early in the twentieth century but suffered a severe setback with the advent of a widespread sponge disease in the 1930s. Rum-running to the United States, a lucrative enterprise, ended with the repeal of Prohibition. World War II created a demand for migrant agricultural laborers to fill jobs abandoned by Americans newly recruited into industry and the military, and Bahamians seized the opportunity to "go on the contract" on the U.S. mainland. The most enduring prosperity for the Bahamas has come from tourism; New Providence has evolved from a wintering place for the very wealthy, as it was in the nineteenth century, to the center of a massive tourist industry that it is today.