Between 1875 and 1876, the army built this installation for heavy guns, known as the North Battery, to strengthen the military effectiveness of Fort Trumbull. Designed for five cannon aimed toward the water, the battery contained four gun platforms located between earthen mounds, and a fifth platform placed just north of the row of mounds. The cannon projected over a granite wall fronted by an earth embankment that shielded the troops from enemy fire. The mounds provided further protection, and two of them housed magazines, chambers for storing ammunition.
Although intended for "the heaviest modern guns," according to an 1879 army plan, the platforms stood empty until the late 1890s, due to changes in military policy and a lack of funds. The army finally installed three heavy guns, called 15-inch Rodmans, in the late 1890s. These huge cannon could pivot in a semicircle to aim up- or downriver.
When it was designed, in the mid-nineteenth century, the 15-inch Rodman gun was the most powerful cannon in the world. It remained a standard weapon for American coastal defense into the 1880s and continued in limited use into the early twentieth century. By the time the Rodmans were installed here, they were becoming outdated.