Franklin and Armfield Office - Credit: Wikimedia Commons
The Franklin and Armfield Office, which houses the Freedom House Museum, is a historic commercial building in Alexandria, Virginia (until 1846, the District of Columbia). Built c. 1810–1820, it was first used as a private residence before being converted to the offices of the largest slave trading firm in the United States, started in 1828 by Isaac Franklin and John Armfield. Another source, using ship manifests (lists of slaves) in the National Archives, gives the number as "at least 5,000". Read more on Wikipedia
Source: en.wikipedia.org