First Mega Church?

This morning I was reading the most recent copy of SMITHSONIAN magazine (December 2015), and came upon an interesting article on the whaling business in Nantucket Island near Massachusets.  The artice is "Quakers with a Vengeance," written by the author of the book and new film "In the Heart of the Sea."  Anyway, in this article the author mentions that in about 1792 there was an immense Quaker meeting house on the corner of Main and Pleasant streetsin Nantucket.  The article says "Instead of an exclusive place of worship, the meeting house was open to nearly anyone. One visitor claimed that almost half those who attended a typical meeting (which sometimes attracted as many as 2,000 people—more than a quarter of the island's population) were not Quakers" (p. 24). Interesting, right?  A mega church of 2,000 on a small island in 1792. Plus, it was open to nearly anyone.  Was this also the first "seeker friendly" church? Could this be the first mega church in the newly formed America?  -Gary McIntosh