Minot's Ledge Light stands on a hazardous reef about a mile off Cohasset and Scituate, where repeated shipwrecks prompted construction of a lighthouse. An iron-pile tower built between 1847 and 1850 on the narrow, mostly submerged ledge soon proved too weak; after warnings from keeper Isaac Dunham and storm damage, it collapsed in April 1851, killing assistant keepers Joseph Wilson and Joseph Antoine as they kept the light and bell going. A far stronger granite tower, designed under Joseph G. Totten, was built from 1855 to 1860 and became the most expensive lighthouse yet constructed in the United States. Its later 1-4-3 flash pattern gave it lasting fame.