Notes on Seneca Quarry & Stonecutting Mill

Reference in C&O Canal Companion: Mile 22.8

Detail from map of Seneca area prepared by
the Historic American Building Survey.

Additional Notes

The sandstone quarry is located on C&O Canal turning basin, but stone was quarried here long before the canal was built. In fact, quarrying had begun even before the American Revolution.

During the 1790s, stone from this quarry was boated down the Potomac through the Seneca skirting canal to the locks under construction at Great Falls and Little Falls. The quarry was owned by the Peter family, who lived in Georgetown during the winter months and were close friends of George Washington. During the construction of the Federal City in the 1790s, George Washington was an occasional overnight guest at the home of Thomas Peter in Georgetown. (Thomas Peter married Martha Washington?s granddaughter.)

The quarry?s proximity to the canal made it an obvious source of stone when construction began on the lower sections of the canal in 1828. However, the canal company first had to negotiate with John P.C. Peter to obtain land for the aqueduct on the west bank of Seneca Creek. A series of court decisions finally resulted in a payment of $2,143.50, which included rights for the company to quarry 20,000 cubic yards of materials from the adjacent land owned by Peter (the sandstone quarry at Seneca). Under the agreement, the canal company had 27 months to quarry the stone, and apparently made good use of the opportunity: the aqueduct over Seneca Creek and Locks 15-26 are largely constructed of the distinctive reddish stone from Seneca.

In 1837 a sawmill was erected near the quarry, using water power from the canal basin to drive eight-foot long band saws that could cut one inch of stone per hour. Stone was brought from the quarry to the sawmill on a narrow-gauge track. The sawmill also cut stone from upstream quarries on Goose Creek (Loudoun County) and Whites Ferry. The mill was probably first powered by a water wheel, which was supplanted by a more advanced turbine. The National Park Service?s illustration of the sawmill (pages 68-69 of the Park Handbook) suggests that water was brought from the canal turning basin into the back of the building by a wooden trough. The water then ran from the sawmill into Seneca Creek.

Plan of Seneca stonecutting mill
the Historic American Building Survey.

When construction began on the Smithsonian ?castle? building in 1847, Seneca sandstone was selected by the Building Committee because of its resistance to weathering as determined by chemical testing. (See the report below.)

As the better-quality stone was eventually depleted, the quarry closed for the last time in 1900. The red sandstone walls of the stonecutting mill still stand near the canal turning basin.




December 7, 1847

The Board will perceive that the Committee, in discharge of their duty, were led into a somewhat extended field of inquiry, especially as regards building material ; and that they have been enabled to collect, and have duly recorded, a large amount of detailed information on this subject essential to their own guidance, but also, they believe, important to the public generally, and especially to the Government, if Congress should decide to erect any other public buildings in this city. They caused to be examined the various marble, and granite, and freestone quarries within a moderate distance of Washington, having been fortunate enough to engage the services of a gentleman of practical experience as a geologist, and who tendered these services gratuitously, his necessary travelling and other expenses only being paid.

The examination embraced the chief marble and granite quarries of Maryland ; the freestone quarries of Acquia Creek, Virginia, whence the material has been drawn for the construction of the Capitol, President's house, Treasury Building, and other public structures in this city ; and the freestone quarries of the upper Potomac, chiefly in the vicinity of Seneca Creek, on the banks of the Chesapeake and Ohio Canal, and about twenty-three miles from the city.

The results of this examination, as contained in the reports made by the geologist, and which will be found spread at large on our journal, were briefly these:


3d. That the Acquia creek freestone, heretofore used in public buildings in Washington, is a material not to be trusted to, being pervaded by dark specks of the protoxide and peroxide of iron, which in peroxidating acquire a yellowish or reddish color, and having occasional clay holes, such as disfigure the Treasury and the Patent Office. A portion of this freestone was, indeed, considered durable and free from material blemish ; but the chance of actually procuring it free from disfiguring spots and stains, was considered so uncertain, that is was recommended to refrain from using it in the Institution building.

4th. That the freestone of the upper Potomac, in the vicinity of Seneca creek, and found in quarries close to the line of the Chesapeake & Ohio Canal, is the best and most durable of all Potomac freestone.


Text excerpted from the Appendix to Hints on Public Architecture, by Robert Dale Owen , published by George P. Putnam, New York, 1849 [Robert Dale Owen was a Congressman and Chairman of the Building Committee of the Smithsonian Institution.]

Photos of Smithsonian Castle building by M High.


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