Expanding on what Jamie Brothers wrote, the iron industry in the Chesapeake
and Delaware drainages started as a primarily Quaker enterprise. The
shareholders in the Bristol and Principio companies were Quaker iron
merchants. Durham Furnace, Pennsylvania, was an enterprise of Quaker
merchants in Philadelphia. From these origins, the later Quaker ironmasters
(notably Isaac Zane) radiated out into the western parts of Virginia and
Pennsylvania.

Because they were so dominant in some colonies, Quaker beliefs had
influence on sites beyond their immediate control, so it might be difficult
to create a model that will distinguish between Quaker and non-Quaker
sites. For example, in Anglican Virginia, wealthy people typically were
buried with elaborate tombstones. In Quaker-dominated Delaware, even the
Anglicans were buried without any permanent grave markers whatever.