Beneath what is now Leetsdale Industrial Park, early industrialists made bricks in a sprawling complex begun in the 1850s.
About 7,000 years earlier, on the same site, American Indians had a settlement on what was then the high area of an island in the Ohio River.
Archaeologists found hundreds of artifacts and clues to the area's history at the 12-acre dig along the bank of the Ohio River in the Industrial Park. The dig was undertaken as a result of construction of a fabrication site for the new Braddock Dam, which was completed and floated down the Monongahela River last year.
Conrad Weiser, environmental resources planner for the Army Corps of Engineers, said artifacts as much as 7,000 years old were found on the site, with most of the material dating from about 1,000 B.C. to 4,000 B.C.
"There's two components to the site," Weiser said. "One's a historic component, which was a brickworks that dated from the 1850s to 1905. And there's the prehistoric component -- the upper portion of the site was largely disturbed by the brickworks, but what we found intact was from maybe the time of Christ back 7,000 years."
Archaeologists said the site was frequently flooded, leaving behind "time capsules" because new soil sealed off the older surface and items left by the people who had used it. About 7,500 years ago, the ground surface would have been about 14 feet lower than it is now, experts said.
Discoveries in the brickworks, which was owned by the Harmonist Society, a German separatist religious group, helped explain developments in brickmaking technology. For example, in its last years the plant had a drying tunnel, in which steam heat was blown on the bricks. That saved time and increased production.
The area was inundated by the flood of 1907, five years after the Harmonists sold it to James Oliver for real estate development, the Corps said.
Going back even further -- and down even deeper -- specialists found arrowheads, dating to about 1,800 B.C., that are typically found in Illinois, Indiana and the lower Ohio River Valley. The Leetsdale discovery could indicate that a group of American Indians from the Midwest traveled up the Ohio River and camped at the site
Archaeologists dug down about 20 feet to the glacial gravels that lie beneath most of Southwestern Pennsylvania.
They found American Indian arrowheads; a sandstone bowl; soapstone, which is not indigenous to Pennsylvania; fire pits; and what appeared to be the bones of a bobcat.
Archaeologists also will test soil samples for pollens and other natural sediments to determine an overall geological makeup of the area.
The Army Corps spent about $6 million for the archaeology work, Weiser said.
Christine Davis, a Verona-based archaeologist, said discoveries of artifacts along the rivers are common, but the extent of the finds at Leetsdale was surprising.
Mindy See, a project manager and researcher for Christine Davis Consultants, said the Leetsdale site is part of a "huge" Indian presence in Southwestern Pennsylvania. Weiser said that until all of the information is catalogued and digested, officials won't be able to say how many people inhabited the island.
Davis said the time period fits the time that the Adena Indians were prevalent in the region.
The Adenas are known for a large burial mound for which Moundsville, Ohio, is named.
See said sites such as the one found in Leetsdale are important because the industrial nature of Pittsburgh has erased much of the historical record.
"A lot of stuff has been obliterated by construction of the city," she said. "But there still is the possibility of finding intact a site like Leetsdale."
Weiser said all of the items removed from the site are being cataloged and analyzed. A final report will be written and submitted to the Army Corps of Engineers for review, and the artifacts will be displayed at the Pennsylvania State Museum in Harrisburg.
However, the archaeological dig is not being preserved. Because the land is private property, the site is being filled and returned to the condition it was in before the Corps needed it.
