(p. 87) Washington proved an excellent businessman, first as a canny speculator in western lands, then as lord of Mount Vernon. Sometimes buying human cargo directly from the holds of slave ships, he came to own more than one hundred slaves by the Revolution and expanded his estate until it encompassed thirteen square miles. An innovative farmer, he invented a plough and presided over a small industrial village at Mount Vernon that included a flour mill and a shop for manufacturing cloth, an entrepreneurial bent that appealed to Hamilton.
Source:
Chernow, Ron. Alexander Hamilton. New York: The Penguin Press, 2004.