The Historic Morrisville Society's Summerseat Building was Thomas Barclay's circa 1765 Georgian mansion and Washington's headquarters in December 1776. Subsequent owners include Declaration of Independence and Constitution signer, Robert Morris. Groups are welcome at the restored National Historic Landmark.
- Days & Hours of Operation: Open to the public the first Saturday of every month 10am – 1pm. Free tours also available by appointment. Visit website for special event dates & times.
- Gift Shop: