Many of them especially those standing in or above the water are obvious engineering achievements. Pick most any point or shoal on the Chesapeake Bay where the earliest of the 61 lighthouses stood, and you ll see a progression of changes and improvements as flaws were found in the old building systems. Take Smith Point Light off Virginia s Northern Neck, for instance. A tower was built at water s edge in 1802, then moved in 1807 away from the eroding shoreline. The second tower was supplemented by an offshore lightship in 1821.
Lightships are simply ships moored into place with lights on top.
The lightship was destroyed by Confederate raiders in 1861, and the second tower on land was replaced with a third tower in 1828, again because of erosion. The seven orders referred to the sizes, the first order being the largest. The Smith Point light tower was again replaced with a new lightship in 1859, and this lightship was replaced by the new screwpile-style lighthouse in 1868. Screwpile lighthouses are built on pilings literally screwed deep into the bedrock. This structure suffered the fate of many screwpile lighthouses on the bay when it was damaged by ice in 1893, repaired, then knocked completely off its pilings and carried away by ice floes in 1895.