Jed Levin, an archaeologist with the National Park Service, which is conducting the dig in partnership with the city, noted that "one important component" of the project "is the exploration of the racial and racist legacy that allowed human bondage" at the birth of the nation.
"In that context, this [pipe bowl] has relevance in a concrete and material way," Levin said. "It demonstrates the continuing legacy of racism."
Levin and other archaeologists speculated that the pipe and fragments were breakage tossed into the basement of one of the commercial buildings erected on the site after demolition of the President's House in 1832.
Levin said such "Negro-head pipes" and other decorative pipes were quite popular in the middle of the 19th century.
In a related development, Independence National Historical Park officials said the excavation site would remain open this weekend from 9 a.m. to 5 p.m. to accommodate burgeoning public interest in viewing the work.
A public platform has been erected on Market Street. Park rangers will be on hand to describe what has been uncovered so far.
Previously open only on weekdays, the site was opened last weekend and drew 1,000 visitors, officials said.
Next week, archaeologists expect to begin excavating so-called shaft features on the site - old wells and privies.
If any artifacts from the time of Washington and Adams have survived, they could turn up in those locations.
Contact culture writer Stephan Salisbury at 215-854-5594 or firstname.lastname@example.org