Although the United States won the War of 1812, the searing memory of the nation's capital in flames continued to disturb the public and Congress alike. The British had entered the Chesapeake Bay, continued up the Potomac River, and set fire to Washington, D.C., in 1814. The need for stronger coastal fortifications was very clear.
President James Madison told Congress in 1815 that "a certain degree of preparation for war . . . affords also the best security for the continuance of peace." He urged Congress to support funding to "improve harbor defense." James Monroe, then secretary of war, shared the president's opinion and told a Senate committee, "It is our duty to put these [vulnerable] ports in a proper state of defense now that we have a fair opportunity to do it." Congress agreed, and for the first time, the United States initiated a fortification program for the coastline in a climate of peace, rather than in a period of international tensions.
Together Madison and Monroe laid the groundwork for what became known as the Third System of coastal fortification, a comprehensive network of seacoast forts, designed and build over several decades starting in 1816. An appointed board of engineers planned and oversaw the building program, with the expectation that the new system of forts would become permanent defenses.
The present Fort Trumbull was built as part of the Third System between 1839 and 1852, under the direction of Captain George Cullum of the Army Corps of Engineers. The Board of Engineers planned for this fort to coordinate with the water battery at Fort Griswold across the Thames River to defend New London Harbor.