From page 298 of Jack Weatherford’s Indian Givers: How Native Americans Transformed the World:
In the 1975 excavation on the White House lawn for the presidential swimming pool, builders found Indian relics that pointed to the commercial prosperity of a former Indian group. Only a few blocks away from the White House, the Indians had operated one of the largest Indian quarries for steatite or soapstone. Numerous manufacturing sites surrounded it where Indian craftsman made dishes, pipes, and implements from the soft stone. From here the Indians traded the manufactured goods all along the eastern coast in what may have been the last productive enterprise practiced by humans along this stretch of the Potomac.
I recommend the book. Very few people have an appreciation of how much of our modern lives was shaped by the indigenous peoples of the Western Hemisphere.