Entitled: "A slave-coffle passing the Capitol" engraving showing slaves wearing handcuffs and shackles passing the US Capitol, around 1815. A coffee is defined as a group of animals, prisoners, or slaves chained together in a line. The Atlantic slave trade took place across the Atlantic Ocean from the 16th through to the 19th centuries. The majority of those enslaved that were transported to the New World, were West Africans from the central and western parts of the continent sold by West Africans to Western European slave traders, or by direct European capture to the Americas. Slavery in the US was the legal institution of chattel slavery that existed in the USA in the 18th and 19th centuries. The US was polarized by slavery into slave and free states along the Mason-Dixon Line, which separated Maryland (slave) and Pennsylvania (free). Although the international slave trade was prohibited from 1808, internal slave-trading continued at a rapid pace, causing the forced migration of more than one million slaves from the Upper South to the Deep South in the antebellum years. The total slave population in the South eventually reached four million before abolition.