Historic Summerseat Historic Summerseat About Historic Summerseat JOIN US FOR OUR NEXT UPCOMING EVENT AT SUMMERSEAT About Summerseat Few homes in America have been owned by or occupied by such important actors of the eighteenth century as Summerseat. Summerseat was General George Washingtons Headquarters in December 1776 owned by two signers of both the Declaration of Independence and the American Constitution Robert Morris and George Clymer. During General Washingtons time there Summerseat was owned by Thomas Barclay who would become Americas first consul overseas and who also negotiated the first treaty for the United States with a foreign nation Morocco. John Adams and Thomas Jefferson with whom Barclay worked while in France recommended Barclay for this position.