Toward the end of the eighteenth century slavery began to show itself unprofitable in the South. The best and most accessible land was exhausted. Except for the rice plantations of South Carolina and Georgia, slavery was not paying. The Southern delegates to the Constitutional Convention, with the exception of the delegates from these states, were prepared to abolish the slave trade. Some of them were ready to free their own slaves. Then came the invention of the cotton gin and the rise of the cotton kingdom. The amount of raw cotton consumed by England was 13,000 bales in 1781; 572,000 bales in 1820; and 3,366,000 bales in 1860. During that period, the South was almost the sole source of supply. The attitude of the South, confronted by this wave of slave prosperity, underwent a complete change. Her statesmen had consented, between 1808 and 1820, to severe restrictive laws directed towards the slave trade. After cotton became king, slaves rose rapidly in price; land, once used and discarded, was again brought under cultivation; cotton-planting spread rapidly into the South and Southwest; Texas was annexed; the Mexican War was fought; an agitation was begun for the annexation of Cuba, and Calhoun (1836) declared that he "ever should regret that this term (piracy) had been applied" to the slave trade in our laws.[25] The change of sentiment corresponded with the changing value of the slaves. Phillips publishes a detailed table of slave values in which he estimates that an unskilled, able-bodied young slave man was worth $300 in 1795; $500 to $700 in 1810; $700 to $1200 to in 1840; and $1100 to $1800 in 1860.[26] The factors which resulted in the increased slave prices were the increased demand for cotton, the increased demand for slaves, and the decrease in the importation of negroes due to the greater severity of the prohibitions on the slave trade. 5. _Slavery for a Race_ The American colonists needed labor to develop the wilderness. White labor was scarce and high, so the colonists turned to slave labor performed by imported blacks. The merchants of the North built the ships and carried on the slave trade at an immense profit. The plantation owners of the South exploited the Negroes after they reached the states. The continuance of the slave trade and the provision of a satisfactory supply of slaves for the Southern market depended upon slave-catching in Africa, which, in turn, involved the destruction of an entire civilization. This work of destruction was carried forward by the leading commercial nations of the world. During nearly 250 years the English speaking inhabitants of America took an active part in the business of enslaving, transporting and selling black men. These Americans--citizens of the United States--bought stolen Negroes on the African coast; carried them against their will across the ocean; sold them into slavery, and then, on the plantations, made use of their enforced labor.