Lighthouses are fairly high maintenance structures, being subject to marine air and the erosional effects of wave and ice. Unmanned structures were also found vulnerable to vandalism and theft. Therefore, automation of many lights led to their effective demolition. The screw-pile lighthouses of the Chesapeake Bay region were particularly vulnerable due to their wood construction, and only four of these survive out of the several dozen constructed; and of these, only the Thomas Point Shoal Light stands at its original location, the other three having been moved to museum settings.