Fort Johnson was built by Sir William Johnson, Baronet, in 1742 and was occupied by him from 1742 to 1763, then by his son Sir John Johnson from 1763 to 1774. Sir John Johnson had himself been knighted in 1735 and became baronet at his father's death on July 11th, 1774. Lady Johnson, the "Lovely Polly" Mary Watts, was distinguished in the society of colonial New York, Canada, and Great Britain for her beauty and social and intellectual gifts, and she occupied this mansion with her brother Major Stephen Watts, who was second in command under Sir John Johnson at Oriska, New York, where he was almost fatally wounded. Major General John Watts de Peyster, great-nephew of Lady Johnson and of Major Stephen Watts and the last Patroon of lower Claverack Manor in Columbia County, New York, purchased Fort Johnson and presented it to the Montgomery County Historical Society on Nov. 9th 1905.
