The Seneca Quarry was the source of stone for two Potomac River canals, the Potomac Company and the Chesapeake and Ohio Canal Company (1780s to 1820s), and for the Smithsonian Institution (1847-1848). After its construction, the C&O Canal was often used to transport the stone from the quarry. Water from the canal was also diverted to provide power for the machinery used to finish the rough blocks. By 1900, quarrying operations at the Seneca Quarry had stopped. The quality of the remaining stone had deteriorated beyond the point of usefulness.
Great photo:
[url]http://www.marylandhistoricaltrust.net/nr/NRDetailPhoto.aspx?propertyName=Seneca%20Quarry&photoLocation=nr161p.jpg[/url]