Minots Ledge Light

Postcard of Minots Ledge Light, c 1905
Postcard of Minots Ledge Light, c 1905
Minots Ledge Light, though not actually in Boston Harbor, is part of the historical lore associated with navigational aids in the harbor and therefore merits consideration as part of the historical context of those aids.

Minots Ledge Light is near the Cohasset Rocks about a mile off Cohasset and Scituate. The rocks had been the scene of many shipwrecks, including 40 just between 1832 and 1841. So, in 1838, the Boston Marine Society formed a committee to study the feasibility of a lighthouse in that location. After the committee reported that a lighthouse was indeed practical, the society repeatedly petitioned Congress to build it. Congress finally appropriated the funds in 1847. The site chosen was a rock known as the Outer Minot, a 25-foot-wide stretch of rock that was exposed only at low tide on calm days and would make the lighthouse the first one in the country in a wave-washed location. Capt. William H. Swift of the War Department’s Topographical Engineers, the designer, thought a stone tower could not be built in such a location so designed a 70-foot-tall tower on nine iron pilings cemented into five-foot-deep holes drilled into the rock. The keeper’s house and lantern were built on top of these pilings, and the entire structure was far less expensive than a stone tower would have been, which must have pleased Pleasonton (D’Entremont 2007j; Witney 1975:44).

The iron lighthouse on Minots Ledge went into operation on January 1, 1850. In storms, the structure reportedly swayed as much as two feet in either direction. The first keeper thought the structure so unsafe he quit after 10 months and the second keeper also expressed grave reservations about its safety. Then, on April 17, 1851, a huge storm completely destroyed the tower, killing the two assistant keepers who were manning it at the time—all that was left the next morning were a few bent pilings sticking out of the rock (D’Entremont 2007j).
Minots Ledge Light during storm surge
Minots Ledge Light during storm surge
While a new lighthouse was being constructed, a lightship was anchored off Minots Ledge from 1851 to 1860. The new Minots Ledge Light, built under the U. S. Lighthouse Board, was designed by Gen. Joseph G. Totten of the army Corps of Engineers with modifications by Capt. Barton S. Alexander, who supervised the work. The tower was to be built of interlocking granite blocks, each anchored to those above and below with massive iron dowels. Work began in July 1855. First the ledge was leveled to accommodate the seven huge granite blocks that formed the foundation. Because construction could only be done at low tide on calm days, the stones were cut and assembled on Government Island in Cohasset Harbor, which by then was attached to the mainland. Each stone was notched to fit the adjacent ones and the tower erected on shore. It was then dismantled and the stones hauled by oxen to a vessel that transported them to the ledge. The first granite block was laid on the ledge in July 1857, the cornerstone in October 1858, and the last stone in June 1860, creating an 89-foot tower the first 40 feet of which was solid except for a central cistern. This base was topped by a hollow tower containing a storeroom, work space, and living quarters (a real keeper’s house was built on Government Island in 1858), and finally surmounted by a bronze lantern whose rooftop finial was about 108 feet above the base. A second-order Fresnel lens was installed in the lantern and the lighthouse went into operation on November 15, 1860 (D’Entremont 2007j, Witney 1975:44-45).

Changes to Minots Ledge Light since that time have included the installation of a rotating mechanism for the Fresnel lens in 1894, making it a flashing light. Its flash was 1-4-3, which someone decided stood for “I love you,” so Minots was nicknamed the “I Love You Light.” In 1947 the Coast Guard automated the light, powering it by batteries. An underwater cable was installed in 1964 and at that time the second-order Fresnel lens replaced with a third-order. When the cable was damaged in a storm in 1971, the light was again powered by batteries until converted to solar power in 1983 (D’Entremont 2007j, Lighthouse Friends 2001a).

Prepared by Nancy S. Seasholes, 2009


Last updated: February 26, 2015

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