It was more difficult to carry out a policy of emancipation when slaves were quoted in the market at a thousand dollars than when the price was a few hundred dollars. All slave-owners felt richer; emancipation appeared to involve a greater sacrifice. Thus the cotton industry went far towards accounting for the changed attitude of the entire country on the subject of slavery. The North as well as the South became financially interested. It was not generally perceived before it actually happened that the border States would take the place of Africa in furnishing the required supply of laborers for Southern plantations. The interstate slave-trade gave to the system a solidarity of interest which was new. All slave-owners became partakers of a common responsibility for the system as a whole. It was the newly developed trade quite as much as the system of slavery itself which furnished the ground for the later anti-slavery appeal. The consciousness of a common guilt for the sin of slavery grew with the increase of actual interstate relations. The abolition of the African slave-trade was an act of the general Government. Congress passed the prohibitory statute in 1807, to go into effect January, 1808. At no time, however, was the prohibition entirely effective, and a limited illegal trade continued until slavery was eventually abolished. This inefficiency of restraint furnished another point of attack for the abolitionists. Through efforts to suppress the African slave-trade, the entire country became conscious of a common responsibility. Before the Revolutionary War, Great Britain had been censured for forcing cheap slaves from Africa upon her unwilling colonies. After the Revolution, New England was blamed for the activity of her citizens in this nefarious trade both before and after it was made illegal. All of this tended to increase the sense of responsibility in every section of the country. Congress had made the foreign slave-trade illegal; and citizens in all sections gradually became aware of the possibility that Congress might likewise restrict or forbid interstate commerce in slaves. The West Indies and Mexico were also closely associated with the United States in the matter of slavery. When Jamestown was founded, negro slavery was already an old institution in the islands of the Caribbean Sea, and thence came the first slaves to Virginia. The abolition of slavery in the island of Hayti, or San Domingo, was accomplished during the French Revolution and the Napoleonic Wars. As incidental to the process of emancipation, the Caucasian inhabitants were massacred or banished, and a republican government was established, composed exclusively of negroes and mulattoes. From the date of the Missouri Compromise to that of the Mexican War, this island was united under a single republic, though it was afterwards divided into the two republics of Hayti and San Domingo.