His father had served under Gustavus Adolphus of Sweden, and pursued a somewhat tortuous course through the troubles of the English civil war, and his maternal grandfather was Sir Robert Gordon, 1st Baronet of Gordonstoun.
[1] Barclay is believed to have first arrived in East New Jersey about 1682, but returned to Great Britain in 1683 bearing correspondence to the Proprietors from Deputy Governor Thomas Rudyard and Surveyor General Samuel Groom.
In 1692 and 1693, John Barclay served in the East New Jersey General Assembly, representing the Town of Perth Amboy.
On November 25, 1695, Barclay was appointed Deputy Provincial Secretary and Register, succeeding Thomas Gordon, who had returned to Great Britain.
Together, they were the parents of two sons:[6][7] John Barclay's later years were spent in Perth Amboy in East New Jersey, where he died on April 29, 1731.