Meanwhile the vast territory included within the Valley of the Mississippi and known at that day as the "Colony of Louisiana," was, in 1803, acquired to the United States by purchase from the French--to whom it had but lately been retroceded by Spain. Both under Spanish and French rule, Slavery had existed throughout this vast yet sparsely populated region. When we acquired it by purchase, it was already there, as an established "institution;" and the Treaty of acquisition not only provided that it should be "incorporated into the Union of the United States, and admitted as soon as possible, according to the principles of the Federal Constitution," but that its inhabitants in the meantime "should be maintained and protected in the free enjoyment of their liberty, property, and the religion which they professed"--and, as "the right of property in man" had really been admitted in practice, if not in theory, by the framers of that Constitution itself--that institution was allowed to remain there. Indeed the sparseness of its population at the time of purchase and the amazing fertility of its soil and adaptability of its climate to Slave Labor, together with the then recent invention by Eli Whitney, of Massachusetts, of that wonderful improvement in the separation of cotton-fibre from its seed, known as the "cotton-gin"--which with the almost simultaneous inventions of Hargreaves, and Arkwright's cotton-spinning machines, and Watt's application of his steam engine, etc., to them, marvelously increased both the cotton supply and demand and completely revolutionized the cotton industry--contributed to rapidly and thickly populate the whole region with white Slave-holders and black Slaves, and to greatly enrich and increase the power of the former.