The most dramatic incident was the sinking of a ship "St John" in October 1849[6] with ninety-nine Irish immigrants, who all drowned within sight of their new homeland.

With extensive experience building fortifications, Totten fully appreciated the permanency and strength of granite constructions.

Working on the ledge could take place only in conditions when it was exposed at low tide and the sea was calm, so construction took years.

The lighthouse is built of large and heavy dovetailed granite blocks, which were cut and dressed ashore in Quincy and taken to the ledge by ship.

The light signal, a 1-4-3 flashing cycle adopted in 1894, is locally referred to as "I LOVE YOU" (1-4-3 being the number of letters in that phrase), and it is often cited[9] as such by romantic couples within its range.

Between 1817 and 1847, it was estimated that 40 lives and $364,000 in property had been lost in shipwrecks in the vicinity of Minots Ledge, off Cohasset, Massachusetts.

William H. Swift, of the United States Topographical Bureau, who recommended an iron-pile lighthouse as offering less resistance to the waves than a stone tower.

The ledge was barely 20 feet (6.1 m) wide and was exposed at low tide, being dry only 2 or 3 hours a day.

The work was conducted from a schooner which remained near the ledge, unless the sea was rough, with the workmen sleeping on board.

Work had to be stopped for the winter in October 1847 and begun again in the spring of 1848, but by September of that year the nine holes had been drilled and the nine iron piles placed.

Braces planned to strengthen the lower part of the tower were omitted on the theory that they would lessen rather than increase the over-all security of the edifice.

The first keeper, Isaac Dunham, was confident the light structure was not safe and wrote Washington requesting that it be strengthened.

A terrific northeast storm a few weeks after he took charge, changed Bennett's mind and he officially reported the tower as in danger.

When he sought to return next day, too heavy a sea was running at Minots Ledge to permit the attempt.

At Minots Ledge, the two assistant keepers kept the bell ringing and the lamps burning, but just before midnight on the 16th they cast a bottle adrift containing a message for the outside world in case they failed to survive.

Plans for a new stone edifice were meanwhile drawn up for the Lighthouse Board by Brigadier General Joseph G. Totten; model makers built the proposed new structure in miniature; the same location was decided upon; and Barton S. Alexander, of the United States Engineers, started work on its construction in April 1855.

The framework structure disappeared during a severe storm on January 19, 1857, when the barque New Empire, which later went ashore at White Head, struck the temporary tower and demolished the iron scaffolding.

Temporary cofferdams were constructed from sand bags, so that the foundation blocks, laid more than 2 feet (0.61 m) under the surface of the lowest tide, could be cemented to the rock face of the ledge.

By the end of 1859, the thirty-second course, 62 feet (19 m) above low water had been reached, and 377 actual crew working hours had been consumed.

On some occasions the seas have actually swept over the top of the 97-foot (30 m) structure with no more damage than that caused by a few leaky windows or a cracked lamp or two.

[4]Minot's Ledge Lighthouse keepers in 1940: George H. Fitzpatrick, Perc A. Evans, Patrick J. Bridy[10] Minot's Ledge Lighthouse was designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1977.

[14] An image of Minot's Ledge Light has featured prominently on the label of Cohasset Punch, a brand of liqueur popular in Chicago, from 1899 until its discontinuation in the late-1980s.