His firm played a big role in the Irish trade – especially in the export of flax seed and the import of linen and other dry goods.
As time passed, the firm's ships were increasingly seen in the ports of England, southern Europe, the Caribbean, and occasionally the Mediterranean.
[1] Thomas Barclay's first decade in Philadelphia was a time of growing friction with England that began with the Stamp Act in 1765 and he was an early member of the resistance.
[2] He was also elected to the Philadelphia Corporation in 1774, named a deputy delegate to the Provincial conventions in 1774 and 1775, and appointed to the Pennsylvania Navy Board in 1777.
There, working with minister Benjamin Franklin during the last years of the war, most of Barclay's time was spent in Dutch and French ports arranging the shipment of blankets, clothing and other supplies for General George Washington's troops.
They had been sent to negotiate treaties of friendship and commerce with the maritime states of Europe and the Barbary powers of Morocco, Algiers, Tunis and Libya in North Africa.
Jefferson succeeded Franklin as minister to France in late spring of 1785, and from that time on Barclay worked closely with him on trade and other matters.
The matter was dropped and Barclay obtained for America a rare treaty with a North African power without promise of tribute — large annual payments and/or delivery of military or other goods of value.
In December 1792 he received a letter from President Washington asking him to go to Algiers to ransom Americans being held there and to negotiate a treaty with the ruling dey.