Canal engineers built aqueducts to carry canal boats over rivers and large streams such as Seneca Creek. Eleven aqueducts were needed between this point and the canal’s western terminus at Cumberland, Maryland, all requiring skilled quarrymen and stonemasons and large outlays of scarce capital. The Seneca Aqueduct opened to traffic in 1833 and, along with through-boats from the west, carried substantial local traffic in lime, grain, fertilizer, and sandstone to and from farms and industries around Seneca. Made of red sandstone from nearby bluffs, it became one of the most admired canal structures. Freshets and flooding on Seneca Creek always caused problems, and in September, 1971, almost fifty years after the canal closed, a violent local flood swept away one of the arches. The last locktender at Seneca was Johnny Riley, whose former lock and lockhouse stand at the east end of the aqueduct, and a former boatman recalled that no matter the hour of night, Riley’s lantern would be waving boats ahead.