In 1794, William O’Neale, a native of County Ulster, Ireland, moved from Chester County, Pennsylvania to open a stone quarry at Mount Vernon and one along the western boundary of the city to provide freestone for Washington’s new public buildings. It was grueling work, not only for the hired men and slaves, but also for O’Neale himself. The use of slave labor so frustrated O’Neale that he abandoned the quarries to stake his own claim in the new capital.