The 42 forts America built after 1815

The moat and masonry wall of Fort Monroe, Hampton, Virginia. NPS photo.

The War of 1812 ended in 1815 having demonstrated that the United States could not keep a foreign navy off its own coast. A year later the federal government had an answer, and it was 42 brick and stone forts.

The plan, of which forts were one quarter

The Board of Engineers for Fortifications met in 1816 and recommended four things together: a strong navy, a standing army with a reserve militia, paved roads and canals to move troops and supplies, and a network of coastal forts. Each depended on the others. James Monroe put the case in his second inaugural in 1821:

By these fortifications, supported by our navy, to which they would afford
like support, we should present to other powers an armed front from the St.
Croix to the Sabine, which would protect, in the event of war, our whole
coast and interior from invasion.

What made the Third System third

The First and Second System forts, built between 1794 and 1812, were earth and timber. These were brick and stone, and uniform — which mattered for more than durability. Masonry let engineers design in two features that timber could not carry:

• Casemates — bombproof rooms, which also gave enough structural strength to build up to four storeys
• Embrasures — proper cannon openings

A completed fort could mount 100 or more guns, and a sailing warship had no answer to that.

Construction used both free and enslaved tradesmen and labourers.

Two men designed most of them

General Simon Bernard, a French officer hired by the federal government for his expertise in fortification, led the board. General Joseph G. Totten, a West Point graduate from Connecticut, replaced him. No one else, military or civilian, shaped the Third System as much.

The forts went up along the Atlantic, Gulf and Pacific coasts. On completion most were not garrisoned or armed — they were, for a while, the appearance of military might rather than the thing itself.

Why a republic suspicious of armies built forts

Fear of standing armies runs back to the Revolution, and that fear is the reason the programme had to be argued for. First Lieutenant Henry W. Halleck made the case in 1846, and the argument is about politics rather than engineering:

When once constructed they require but very little expenditure for their
support. In time of peace they withdraw no valuable citizens from the useful
occupations of life. Of themselves they can never exert an influence
corrupting to public morals, or dangerous to public liberty; but as the
means of preserving peace, and as obstacles to an invader, their influence
and power are immense.

A fort cannot march on the capital. That was the point.

The end, around 1867

Steel breech-loading rifled cannon and steel steam-powered warships made masonry obsolete faster than it wore out. No other country built a coastal fortification programme like it, before or after.

Sources

Written from the National Park Service's article on the Third System of coastal forts, a work of the United States government in the public domain, with the Coast Defense Study Group's short history.