Between 1525 and 1866, 12.5 million captive Africans were shipped across the Atlantic Ocean bound for enslavement, and more than 389,000 were transported directly to what became the United States. Nearly one third of those, 129,000 people, were brought through Washington, DC and nearby Maryland and Virginia ports. Strategically located along major water and railroad routes, Washington, DC became a trade and transportation hub where at least seven major slave pens temporarily imprisoned enslaved people until transport south by ship could be arranged. Enslaved Africans built much of the new capital, including the U.S. Capitol and the White House. Visitors expressed disgust at the sight of slave coffles and holding pens in the nation's capital, and in 1846 Abraham Lincoln referred to a slave jail visible from his Capitol Hill boarding house that had been openly maintained for fifty years. All people of African descent, enslaved as well as free, lived in perpetual vulnerability: enslaved people feared sale and separation from family, while free Blacks had to carry certificates of freedom and could be jailed or sold into slavery without proof of status, sometimes having to pay imprisonment costs even after proving they were free. On April 16, 1862, President Lincoln enacted the District of Columbia's Compensated Emancipation Act, abolishing slavery in the District and freeing over 3,000 people while compensating former slaveholders. The Emancipation Proclamation, enacted on January 1, 1863, freed enslaved people in the confederate states, and April 16 was celebrated as a public holiday in Washington, DC from 1866 to 1901 before being reinstated as Emancipation Day in 2004.