This gargantuan engineering effort repeated the idea of Strickland's breakwater (ES25), but on a much larger scale (8,040 feet) and in deeper water. The earlier Breakwater Harbor had succumbed to siltation that accompanied the phenomenal nineteenth-century growth of the Cape Henlopen sand-spit (sixteen feet per year, so that it is now a mile longer than in 1765). The National Harbor of Refuge, well north from that spit, was authorized in 1896 and built from stones up to thirteen tons each. Steam power made the project go ten times faster than Strickland's earlier campaign. The huge steel caisson lighthouse (1926), a tapering white cylinder atop a round black base, still works but has been unmanned since 1973. A volunteer group has begun its restoration.