The Barclay Collection : Papers of the St. Croix Commission and Commissions Following the Treaty of Ghent Appointed to Agree on a Canadian-American Border Between Passamaquoddy Bay and the Great Lakes : 1764 - 1827.

Thomas Barclay (1753-1830) was born in New York City, the son of Rev. Henry Barclay, rector of Trinity (Anglican) Church, and his wife, Mary Rutgers. He was educated at Kings College (now Columbia University), graduating in 1772, and studied law in the office of John Jay. In 1775, he was called to the bar and in the same year married Susanna DeLancey, the daughter of Peter DeLancey and his wife Elizabeth, the daughter of Cadwallader Colden. Thomas Barclay's sister, Cordelia, married Lieutenant Colonel Stephen DeLancey, and his sister, Anna Dorothea, was the wife of Colonel Beverley Robinson of the Loyal American Regiment. Marriages between these and other prominent New York families formed bonds of loyalty to Great Britain which were an important factor in the American Revolution. In 1776, Thomas Barclay joined the British forces, and in 1777 he was commissioned a captain in the Loyal American Regiment. Later, he was promoted to the rank of major and served throughout the war in New York, New Jersey, and in the Southern Campaign in the Carolinas. 

Because he was a Loyalist, all his property in New York was confiscated and sold, and the money from the sale deposited in the state treasury. In fact, it is thought that his property was the first confiscated by the state. In 1779, he was named in the Act of Attainder passed by the New York legislature, and at the end of the war, with thousands of other Loyalists and their families, he was forced to join the refugee migration to Nova Scotia. He received land in Wilmot Township, Nova Scotia, but later moved to Annapolis Royal where he re-established his law practice and immediately became active in the political life of the colony. In 1785, he was elected to the Nova Scotia House of Assembly and in 1793 became Speaker of the Assembly. In the same year, he was named lieutenant-colonel of the Royal Nova Scotia Regiment and adjutant-general of the militia.

The Treaty of Paris in 1783 established the St. Croix River as the boundary between New Brunswick and the United States, and by the fifth article in Jay's Treaty of 1794, a commission was established to clarify which of two rivers emptying into Passamaquoddy Bay was the St. Croix. Governor Wentworth of Nova Scotia recommended Thomas Barclay as the Briish Commissioner, and the negotiations ended successfully for the British in 1798 with the most western river, the St. Croix, being established as the boundary. After a brief return to Nova Scotia, Thomas Barclay was named consul-general in New York in 1799. He remained there until the beginning of the War of 1812 when he was recalled to Britain, only to be sent back to New York in 1813 as the agent for British prisoners of War in the United States.

At the end of the War the issue of the international boundary between New Brunswick and the United States surfaced again, and it was Thomas Barclay who was appointed once more as the British Commissioner under the terms of the Treaty of Ghent. Ward Chipman served again as the British agent. The Commission dealt with two issues: the ownership of the islands in Passamaquoddy Bay, which they agreed upon in 1817, and the extension of the border from the source of the St. Croix River to the St. Lawrence River. When agreement could not be reached, the latter issue was submitted to the King of the Netherlands for arbitration. In 1831, he issued his decision, which was not accepted by either parties, and the final settlement did not come until 1842 with the Webster-Asburton Treaty. Thomas Barclay's participation in the second boundary commission was his last act of public service. Subsequently, he retired to his home in New York where he lived until his death on 21 April 1830. Of his twelve children, at least four sons attended King's College, Windsor, Nova Scotia, including Anthony Barclay (1792-1877), who participated in the second boundary commission, and like his father, became British Consul in New York.