NANTUCKET — Since 1850, the Sankaty Head Lighthouse has guided boaters and pilots home to the east shore of this island. This week, the lighthouse is being steered to a safe harbor of its own.

Much of the cliff where the working lighthouse sits has been eaten away by storms, threatening to send it plummeting into the Atlantic Ocean.

The only original lighthouse left on Nantucket — two others were destroyed and rebuilt — the Sankaty tower with the red band painted around it is viewed by many as a symbol of the island. In keeping with its listing on the National Register of Historic Places, its supporters say, it needed to be preserved, and moving it 405 feet northwest to another site was the only way.