Archaeology done at Fletcher's Boathouse in 1997, before some parking lot construction, located more than 8 large Native storage pits. They seem to have been dug sequentially at roughly the same time, more than 2000 years ago. One theory for their use was that Natives travelling upriver, got to the falls on the Potomac, and stored their excess goods in the pits, before portaging their canoes upstream.
Yet another fascinating piece of DC Native History that goes untold at Fletchers and elsewhere in the city!
Here's a story that ran about the site in the Washington Post, Nov 1, 1998. B6.