At the height of ownership, William owned close to 200 enslaved African-Americans who lived in twenty-five slave quartering buildings on the property.

[4] At William's death, there were 154 enslaved people living at Pharsalia who then fell into possession of his fourth wife, Maria Catherine Effinger (1814-1889), and his children.

Those enslaved at Pharsalia produced wheat, oats, hemp, tobacco, potatoes, bacon, whiskey, wool, apples, and other crops, and raised animals for the Massie family.

William was also a prominent slave barterer, breeder, and seller in addition to owner, keeping meticulous records on those enslaved at Pharsalia and the crops they produced, and occasionally would detail their lives including their deaths and if they were sold and why in his "Negro Book.

[10] Maria also contracted enslaved people at the Pharsalia plantation for laboring and impressment on Confederate fortifications, for horse maintenance and goods production during the war.