Jersey, children born to slave mothers had to serve an extended period of indenture into young adulthood. In other cases, some slaves were reclassified as indentured servants, effectively preserving the institution of slavery through another name. Often citing Revolutionary ideals, some slaveholders freed their slaves in the first two decades after independence, either outright or through their wills. The proportion of free blacks rose markedly in the Upper South in this period, before the invention of the cotton gin created a new demand for slaves in the developing "Cotton Kingdom" of the Deep South. By 1808 (the first year allowed by the Constitution to federally ban the import slave trade), all states (except South Carolina) had banned the international buying or selling of slaves. Acting on the advice of President Thomas Jefferson, who denounced the international trade as "violations of human rights which have been so long continued on the unoffending inhabitants of Africa, in which the morality, the reputation, and the best interests of our country have long been eager to proscribe", in 1807 Congress also banned the international slave trade. However, the domestic slave trade continued in the South. It brought great wealth to the South, especially to New Orleans, which became the fourth largest city in the country, also based on the growth of its port. In the antebellum years, more than one million enslaved African Americans were transported from the Upper South to the developing Deep South, mostly in the slave trade. Cotton culture, dependent on slavery, formed the basis of new wealth in the Deep South. In 1844 the Quaker petition was rediscovered and became a focus of the burgeoning abolitionist movement. Emancipation Proclamation and end of slavery in the US On 1 January 1863, Abraham Lincoln signed Emancipation Proclamation freeing slaves in areas in rebellion during the American Civil War when Union troops advanced south. The Thirteenth Amendment (abolition of slavery and involuntary servitude) was ratified in December 1865. See also Abolitionism in the United States American Descendants of Slavery (ADOS) Atlantic Creole Bristol slave trade Thirteenth Amendment to the United States Constitution Emancipation Proclamation Timeline of abolition of slavery and serfdom Colonial history of the United States Female slavery in the United States Free negro Grand Model for the Province of Carolina History of labor law in the United States History of slavery in Connecticut History of slavery in Florida History of slavery