Through his father, he was a member of the Border Reiver Scottish clan Johnstone and, reportedly, in "middle life he was called upon to receive the title and estate of Marquis of Annandale," a title in the Peerage of Scotland,[b] "but declined on the ground that he was an American and unwilling to give up his birthright for a life in England, but later, at the coming of age of his eldest son, regretted his refusal.
"[2] His maternal grandfather, David Jamison, was one of the so-called Nine Partners who purchased a large tract of land in the Province of New York in 1697.
He worked as a merchant until the death of his mother when he inherited his share of the Nine Partners Tract, which by then was worth a substantial amount, and required his considerable attention as his land and estates were extensive.
[7] In February 1761, he was elected to the New York General Assembly and was registered a Freeman of the City on 21 August 1770 as "David Johnston, Gentleman.
[9] In New York City, he had a mansion on the east side of Bowling Green (which was burned during the Revolutionary War), a farm in Greenwich Village, a farm in Perth Amboy (which was burned by the Hessians when the British Army occupied New Jersey), and in the Hudson Valley, he owned a large country estate and residence known as Annandale in Lithgow (a hamlet within Washington, New York Johnston named after Linlithgow, the ancestral home of his maternal grandfather)[5] where he permanently moved to after the War.