A 1,600-acre chapter of American history is on the market in the Catskills, where a sprawling estate that’s been owned by the same prominent family for more than 200 years just hit the market for $14 million. At the heart of the property stands The Lake House, built in 1787 by Gertrude Livingston and her husband, Col. Morgan Lewis — a Revolutionary War general, New York governor, and confidant of...