Selected Papers From The 1983 And 1984 George Rogers Clark Trans-Appalachian Frontier History Conferences
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Military Architecture on the American Frontier
David A. Simmons
Department Head
Inventory and Registration
Historic Preservation Division
Ohio Historical Society

Fortifications on the Eastern American frontier have long been a subject of interest to historians — but until recently the study of forts has primarily been the domain of antiquarians whose knowledge and understanding of military architecture was limited to whatever local sources and traditions were apparent for a particular fort site. For the serious student of military architecture there is a wealth of resources on frontier fortifications: documentary resources for specific structures, including the correspondence of fort commandants and travelers' observations; information on contemporary fortifications built by the same individuals; and general eighteenth century fortification theory.

This paper proposes to examine these sources to reveal the large variety of options available to the military engineer on the eastern North American frontier during the 18th and early 19th centuries. What principles for example, applied to the construction of frontier forts? How were these principles employed in the actual construction of a primary fort element such as the walls? How did the background of various fort builders influence the design of specific forts?

A starting point for the study of any frontier fortification is with an understanding of the general architectural and theoretical background of European military thought. While it is true that these tenets were modified in America, this was the intellectual baggage brought into the frontier by practically every officer.

European architects and engineers of the 15th century were faced with the introduction of gunpowder into the warfare of the western hemisphere. This technological advance altered forever the character of fortification design. Most immediately it made the traditional stone castle fortification obsolete. Tall stone walls were too easily reduced to rubble by an attacker's artillery. The bastioned system of fortification was developed in Italy in the 15th century in response to this new armament. [1] When viewed with historical perspective, the fortification developed by the Italians to solve this problem was striking in its simplicity: they lowered the whole complex down into the ground. To prevent an enemy from simply walking into the lowered fort, the old moat was retained and developed into an elaborate ditch system. A portion of the dirt from the ditch was thrown to the front to create an earthen slope called a glacis. This aided in hiding the fortification and supposedly provided an absorbing cushion for cannon balls fired by an attacker's artillery or at least harmlessly deflected them. The new fortifications became a "defense in depth" in place of the former emphasis on height. In conjunction with this passive defensive system, a more aggressive method of defense focused around the corner projections known as bastions. From these corner emplacements the troops and artillery of the defenders could bring cross fires upon the attackers outside the fort walls. The round towers common to medieval castles were problematic because they resulted in an undefensible area at their base. The simplest solution was to point the structure and various arrangements on the corners and walls were designed to cover the entire exterior ground of the fort within a certain distance. As a result European fortifications of the 16th, 17th and 18th centuries consisted of remarkably complex series of angles and planes, and an understanding of geometry and adeptness at drawing were the tools of the military engineer's trade. [2] The term bastion came from the French word for fortress, and very quickly the bastion became the prime characteristic of virtually all European fortifications.

The Parts of a Fort. (From Alfred Proctor James and Charles Morse Stotz, Drum in the Forest, ©Historical Society of Western Pennsylvania, 1958.)

Originally the Italians were the leading practitioners of this new bastioned system, but by the 17th century the French acquired a continental reputation for their impressive fortifications. Most prominent among the French military men was Sebastien Le Prestre de Vauban who served as an engineer in Louis XIV's court. Vauban had a reputation of never surrendering a fort and never having failed to take one attacked. In fact it was through his offensive prowess that he made his major accomplishments. Volumes written by him and published in the early 18th century became the standard reference works in the field consulted by military leaders of all nationalities. Subsequent authors borrowed heavily from Vauban's concepts in a sizable array of books on fortification theory and practice. [3] Most included elaborate illustrations that reflected the high development of the bastioned system in Europe. These publications were carried to North America by military officers assigned to the colonies and were translated and adopted by the new United States.

On the American frontier few fortifications reached the sophistication of these European models. William Smith's volume on the Henry Bouquet expedition into Ohio in 1764 contained an outline of the basic principles for forts on the American frontier entitled "Construction of Forts against Indians." The appearance of the outline in manuscript form accompanying some Ohio Valley fort plats in the collections of the Indiana Historical Society attest to its use in the Midwest. It reads in part [4]:

"As we have not to guard here against Cannon, the system of European Fortifications may be laid aside, as expensive, and not answering the purpose. Forts against Indians, being commonly remote from our settlements, require a great deal of room to lodge a sufficient quantity of Stores and provisions, and at the same time ought to be defensible with one half of their compleat Garrisons, in case of detachments or Convoys."

In this statement we can see three basic considerations that should be kept in mind when studying frontier fortifications. First was the public concern, whether it was French, British, or American, for limiting the expense of frontier forts. The claims of frugality made in the correspondence of fort commandants were surpassed only by their superiors' demands for the same. Secondly, these frontier forts were designed principally to house and provide for the movement of stores and supplies. Finally, they had to be defensible by a small quantity of troops.

Another vital concept for what the 18th century military officer termed as "field works" a contemporary term for what we today would call frontier fortifications, was put forward by a French engineer named Clairac who wrote a volume entitled the Field Engineer which was translated and published in Philadelphia in 1776. [5] George Washington had a copy of this work in his own personal library. The concept stated that any soldier defending a fortification generally fires mechanically straight ahead rather than to the right of left.

How was this concept manifested in a specific frontier fort? Lines of musket fire can be projected at right angles from the walls on the plat of Fort Duquesne, built in the middle of the 18th century at present-day Pittsburgh. A cross fire is brought on the area directly in front of the main walls of the fort from firing steps on these walls and from the flanks of the bastions. A larger area is covered from the faces of the bastions. But what of the ground opposite the points or salient angles of the bastions? Since the area was uncovered, ravelins or simple pointed projections were erected in the centers of each wall. Lines of fire from the faces of the ravelins covered the ground before the bastion angles. At Duquesne this was necessary on only two sides, since the Ohio and Monongahela Rivers protected the other sides of the fort and made assault from these directions unlikely. [6]

Following the tenets of Smith's book, Clairac's concept of "lines of fire" and the components of the bastioned system itself did not dictate a single form for frontier fortifications. The outline of the French Fort Duquesne which we examined earlier can be viewed as the "typical" bastioned fort in the frontier. A variation on that trace was the "half-bastion" or demi-basion shown in the plat of Fort Lernoult built by the British at Detroit in 1778. Henry Bird, the engineer for this fort, acknowledged that this trace was less perfect than full bastions, since more area was uncovered on the exterior of the walls. But the open configuration of half-bastions allowed for increased storage space on the interior. More importantly the reduced number of faces and flanks on the bastions made them simpler and quicker to construct and thus less expensive. [7]

The star trace used by the British to build Fort Bull in western New York in 1755 departed even more from the bastioned system by omitting corner emplacements entirely and utilizing "redan" or triangular type structures in the center of each wall. As in the previous example the reduced number of walls lowered the cost and also resulted in a need for fewer garrison troops. In this case it did not work to the advantage of the defenders for French forces captured and destroyed the fort a few months after it was built. [8] The star shape left many areas outside the fort uncovered, but according to one British military writer in the 1780s it was a popular form with Americans at the start of the Revolution, especially since it supposedly was invented by and remained a favorite of the French who assumed the role of military tutors for the new nation. [9]

Military engineers considered the triangular form even less desirable, since it left uncovered with any field of fire significant segments of the area outside the fort. Still it was useful in situations where there were very small garrisons and a shortage of time or money to build a more sophisticated structure. Such was the case at the Pickaway Indian towns near the modern city of Springfield, Ohio, in 1780. Henry Bird, builder of Fort Lernoult, reportedly directed the construction of a triangular stockade and blockhouse at these settlements. A structure with a minimum of walls was optimal in a situation where the discipline and capabilities of the defending troops was limited. [10]

Civilian fortifications, particularly blockhouses, became the norm on the Old Northwest frontier during the War of 1812, because by this time there were a number of substantial areas of settlement. While European military treatises were noticeably silent on the subject, there are many contemporary accounts and drawings of blockhouses, both military and civilian, which describe two-story wooden structures, often but not always, with the second story projecting over the first. [11] A number of these early 19th century military structures are still standing in the northern United States and [12] even more remarkable is the preservation of a civilian blockhouse in Miami County, Ohio, several miles east of Troy. It has perhaps escaped notice in the past because its construction does not fall into the traditional images of a frontier blockhouse. It could perhaps be better classified as a fortified house; it is a two-story residence built of two-foot-thick stone walls. A masonry first story for blockhouses was actually not rare on the frontier, and was, in fact, recommended by some British military officers to increase the durability of a blockhouse and again reduce its long term expense [13]. The Miami County blockhouse was built in 1813 and actually was much more residential in character than military in its overall design and finishes. One major element of the original design was unmistakably military: the inclusion of a kingpost truss in the attic which with wrought iron tie rods supported the load of the second-story floor joists and thus eliminated the need for load bearing walls on the first floor. The open lower story, uninterrupted by walls and with corner fireplaces, was ideal for defensive military activities. [14]

We have seen how the basic fortification concepts developed in Europe were adapted in the American frontier. Taking this a step further, a close examination of one particular structural element will build an appreciation of the design choices available to the military engineer in the late 18th and early 19th centuries in North America, and aid in understanding the exchange and interaction of military ideas on the frontier. The most basic architectural element of an eastern frontier fort was its wall, and there was, in fact, a great variety of construction techniques and devices, so it is perfect for this type of survey.

By far the most common fort wall was the stockade. Contemporary civilian accounts of frontier fort construction like that directed by Ben Franklin in 1756 are replete with descriptions of this type of fortification. [15] It was, of course, ideally suited to the capabilities of a non-military force requiring no special skills beyond an adeptness with an axe and shovel. [16] While it provided a certain sense of security, a single wall stockade was a flawed system. In the first place a single row of logs with one end stuck in the ground produced a highly unstable structure, even with the standard ribband or strip of wood connecting each picket, so that it constantly required attention to provide any defense at all. Secondly, unless great care was taken in selecting the logs and placing them in the trench, there were frequently significant gaps between each log.

Military officers, therefore, insisted on either "lining" the walls with boards to cover the gaps or to add a second row of smaller pickets inside the first row and positioned between the outer row to cover the gaps. By the early 19th century this latter method had become the standard in the fortification classes taught by the U.S. Military Academy at West Point. [17]

The French Fort Maurepas from the late 17th century in the lower Mississippi Valley was clearly built by an insecure colonial power to guard against the incursions of the British. The walls in this case were constructed by the French commandant as a double row of large logs supplemented by a smaller row to the rear. In other words, it was triple stockade intended to defend against light artillery. [18]

An interesting variation to increase the stability of the stockade was designed by British engineers at Fort George in 1799. Here every 14th picket was planted several feet further into the ground than the adjacent pickets and was strengthened with a brace of horizontal and diagonal members at its base. [19]

Another simpler variation on the "standard" stockade wall was used in Fort Necessity, Pennsylvania, constructed by Virginia militia under the direction of George Washington in 1754. The walls of Washington's odd little circular fort were composed of oak logs split in half with smaller posts on the interior to serve as musket rests or to simply fill gaps in the wall. The archaeologist who discovered this design for the National Park Service in the 1930s speculated that this wall may have been unique to Washington and a result of time and personnel shortages during its construction to reduce the quantity of trees that had to be felled. It should be noted, however, that this same wall design was still being used in the southern states 80 years later, so that this technique may, in fact, represent a regional characteristic. [20]

Vertical stockade walls could also be combined with "traditional horizontal log wall building construction to form the outer wall of the fortification. In other words the rear walls of the fort buildings also served as the outside wall of the fort and pickets were used to fill between the buildings. This was a common feature of civilian fortifications or "stations," but was also used in military forts where time constraints were a factor. Such was the case at Fort Jefferson built in 1791 during Arthur St. Clair's ill-fated campaign, only in this case a horizontal log wall construction was utilized for the corner bastions as well. [21]

Perhaps the simplest of all frontier fort walls were those erected by the U.S. Army and Kentucky militia in the Ohio Valley during the 1790s. These "temporary fortifications" were formed by cutting down trees to form a 5-foot high breastwork which one participant called a "brush fence." Occasionally where timber was scarce the walls were formed of earth, but it was done on a daily basis to protect the encamped army from surprise attack. [22]

All of the wall systems were only a defense against the limited armament of Indians and not a European enemy equipped with artillery. To defend against the latter type of attack required a more sophisticated structure intended to absorb the shock of artillery.

Fort Defiance was originally built in modern-day Defiance, Ohio, by the U.S. Army in 1794. It initially had a stockade wall set in a 3-foot trench. Following the Battle of Fallen Timbers and the confrontation with the British fort at present-day Maumee (Fort Miamis), the Army returned to Defiance and began modifying it to account for a European enemy. Archaeological excavations done several summers ago show the distinctive profile of a ditch dug out around the perimeter of the fort and thrown against the wall. [23]

Most horizontal log walls were actually composed of two parallel walls tied together with cross member to form a crib-work and then filled with earth. This system could be used by itself to form the walls of a fort, as at the British designed Fort Ligonier built in 1758; or it might be combined with heavy wooden buildings immediately to the interior which were themselves covered with earth as protection against artillery as at Fort Ontario also built by the British in the late 1750s. [24] Both techniques were intended as a defense against artillery, but since each relied predominantely on wooden forms they were still susceptible to artillery. As a consequence when the enemy was primarily a European one, earthen fortification walls were preferred.

During the 18th century a clear distinction was made by military theorists between regular and irregular fortifications. Regular fortifications technically referred to a work whose defensive structures were all symmetrical and had equal components. there is evidence to suggest, however, that the term regular fortification had an additional meaning to military officers in America. Anthony Wayne, for example, referred to a regular fortification as one defensible against artillery. [25]

To construct an earthen wall fort a wooden framework was prepared under the direction of the engineer. It served no structural function, but rather simply marked the limits of the parapet as a guide for workmen. The dirt for the outer ditch was then dug out and thrown into the framework. As the U.S. Military Academy at West Point developed its programs, officers were trained to calculate the time involved in erecting such a structure by determining how far an individual could throw the earth, and at what rate, depending on the size of the final wall desired. [26]

The earth was unstable by itself and required some physical support to maintain its shape. Sod, cut in slabs and laid like brick was one method of providing a cohesive revetment; in another method the earth was secured with fascines (bundles of sticks); or hurdles (a type of interwoven basketweave frame); or gabion (woven baskets filled with earth), or a scrap revetment formed of dovetailed planks or heavy timber or stone slabs like at Fort Wayne in Detroit. All were covered in detail for officers at the U.S. Military Academy in the early 19th century. [27]

What then can we learn from the study of frontier forts? The first point to make is that too often the concept of frontier fortifications has been vastly oversimplified by historians and an assumption made that one fort was pretty much like another. Even the treatment of forts on the Cis-Mississippi frontier in Willard Robinson's recent book American Forts is relatively cursory and lightweight. As I have tried to indicate, military architecture holds the same potential for information as the study of building types and style distributions normally associated with folklorists and architectural historians. A whole host of various plans, materials, techniques and functions governed 18th and 19th century fort design decisions. Studying the interplay of these elements as displayed in frontier forts can shed light on the spread and adaptation of cultural characteristics between different peoples. What, if any, techniques for example, were unique to the Dutch, French, Spanish, or British engineers who built forts in the American frontier?

Any purely architectural study of course runs the risk of treating structures in an abstract manner separate from their human environment and perspectives. In recognition of this, I have tried to focus on specific individuals when discussing particular forts to emphasize that each was designed through a series of personal decisions based on knowledge, training or experience. There are any number of individual engineers, superintendents of construction and master builder/carpenters who were recognized as "experts" in their field and whose assistance was frequently solicited on new fortifications.

One brief example will demonstrate the validity of this latter approach. William Ferguson was an Irish immigrant who settled in Pennsylvania in the 18th century and enlisted in the Continental Artillery during the Revolution. When the small federal army was created in the 1780s he obtained a captain's commission in the artillery and served at a number of posts in the Ohio Valley. As an artillery officer, Ferguson was frequently called on to provide engineering services for the army, a typical practice of the period. After he was promoted to Major and assigned to Arthur St. Clair's ill-fated army in 1791, he in effect, became chief field engineer on the expedition, responsible for directing the construction of all fortifications. One of the posts Ferguson served at prior to the expedition was Fort Finney at the falls of the Ohio River. One of its distinctive features was a guardhouse positioned in the center of the wall opposite the main gate which projected out from the wall. It should come as no surprise that when Fort Hamilton was built under Ferguson's direction it included a guardhouse placed exactly as that at Fort Finney. An examination of groups of forts erected by and under the guidance of individuals like Ferguson, much as architectural historians have looked at the work of a particular architect, is yet another useful area of study. [28]

The field of military architecture is, therefore, a largely unexplored and promising area for future research.

Conjectural Plan of Fort Hamilton, ca. 1793


1Sebastien Le Prestre de Vauban, A Manual of Siegecraft and Fortification (1740), translation and introduction by George Rothrock (Ann Arbor: University of Michigan Press, 1968), pp. 3-4. The introduction written by Rothrock has a general discussion of the advent of the bastioned system. For a more in-depth discussion see John R. Hale, "The Early Development of the Bastion: An Italian Chronology, c. 1450-c. 1534," in Europe in the Late Middle Ages (London: Faber and Faber, 1965), pp. 466-494. See also Charles M. Stotz, "Defense in the Wilderness" in Drums in the Forest (Pittsburgh: Historical Society of Western Pennsylvania, 1958), pp. 59-197.

2Americans who observed the French engineers operating during the Yorktown campaign in 1781 made note of their "geometrical operations." See James Thomas Flexner, George Washington in the American Revolution (Boston: Little, Brown, & Co., 1967), p. 435.

3Vauban, Manual of Siegecraft and Fortification, pp. vi-xi.

4William Smith, An Historical Account of the Expedition Against the Ohio Indians in the Year 1764 (Philadelphia: William Bradford, 1765); and "Construction of Forts against Indians," Northwest Territory Collection, Indiana Historical Society.

5Chevalier de Clairac, L'Ingenier De Campagne or, Field Engineers, (translated by Major Lewis Nicola) (Philadelphia: R. Aitken, 1776); Richard Ketchum, The World of George Washington (New York: American Heritage, Inc., 1974).

6Stotz, "Defense in the Wilderness," opposite p. 129.

7Willard B. Robinson, American Forts: Architectural Form and Function (Urbana: University of Illinois Press, 1977), pp. 56-57.

8Gilbert Hagerty, "Fort Bull: A Pre-Archaeological Study, Northeast Historical Archaeology, Vol. 2, No. 1 (Spring 1972), pp. 20-21.

9Lochee, Elements of Field Fortification (London: author, 1783), p. 61. An illustration of a star fort is in Captain George Smith, An Universal Military Dictionary (London: J. Millan, 1779), p. 95.

10"Account of Henry Wilson" in J. Martin West, ed., Clark's Shawnee Campaign of 1780 (Springfield: The Clark County Historical Society, 1975), pp. 32-37; "British Account of Bird's Expedition," Draper Mss, State Historical Society of Wisconsin, Madison, 29J19. Interestingly there are some indications that the Indians were more "disciplined" than might ordinarily have been the case. One participant reported their forming into a line of battle and advancing as a group against Clark's troops.

11Two European travelers' accounts which describe blockhouses are Francis Bailey, Journal of a Tour in Unsettled Parts of North America in 1796 to 1797 (London: Bailey Bros., 1856), p. 145; and Isaac Weld, Travels Through the States of North America, and the Provinces of Upper and Lower Canada, During the Years 1795, 1796, and 1797 (London: John Stockdale, 1807), Vol. II, pp. 178-179. Perhaps the best known drawing was in Thomas Anburey, Travels Through the Interior Parts of America (London, 1789). The blockhouses built by the U.S. Army at Fort Fayette at Pittsburgh in 1792 were built with the second story equal in size to the first story, since according to Isaac Craig projecting upper stories resulted in "very Insubstantial Buildings." See Craig to Henry Knox, January 15, 1792, Letterbook II-A, Isaac Craig Collection, Carnegie Library of Pittsburgh.

12Two examples are the American blockhouses at Fort Mackinac on Mackinac Island, Michigan, built between 1798 and 1800, and the West Point Blockhouse at St. Andrews in New Brunswick built in 1812. An especially useful description of British blockhouses in Canada is Richard J. Young, "Blockhouses in Canada, 1749-1841: A Comparative Report and Catalogue," Canadian Historic Sites: Occasional Papers in Archaeology and History, No. 23 (Ottawa: Parks Canada, 1980), pp. 5-116.

13See Patrick Sinclair correspondence in Brian L. Dunnigan, "The Post of Mackinac, 1779-1812" (M. A. thesis, Coopertown, N.Y., 1976), pp. 56-57.

14This was similar to the old State Arsenal built in Columbus, Ohio, during the Civil War and the barracks at Fort Wayne in Detroit dating to 1848. See National Register of Historic Places Inventory and Nomination Form for the John Minor Dye Stonehouse, Troy Vicinity, Miami County, in the Ohio Historic Preservation Office, Columbus. A "fortified house" in Pennsylvania was similar in design to the Dye blockhouse. See James W. Van Stone, "Fortified Houses in Western Pennsylvania," Pennsylvania Archaeologist, Vol. XX, No. 1-2 (Jan.-June 1950), p. 23.

15Thomas Lynch Montgomery, ed., Report of the Commission to Locate the Site of the Frontier Forts of Pennsylvania (Harrisburg: Wm. S. Ray, 1916), pp. 190-194; William A. Hunter, Forts on the Pennsylvania Frontier, 1753-1758 (Harrisburg: Pennsylvania Historical and Museum Commission, 1960), pp. 236-7.

16The concept of a palisade was, one fortification treatise indicated, "ancient even in ancient times" and thus had a long European precedent. See Lochee, Field Fortification, p. 25.

17C. Meigs, "Notes on Course of Field Fortification," Joseph M. Toner Collection, Box 267, Figure 18th, Library of Congress.

18Robinson, American Forts, pp. 24, 26.

19Robert S. Allen, "A History of Fort George, Upper Canada," Canadian Historic Sites: Occasional Papers in Archaeology and History, No. 11, pp. 65-66.

20J. C. Harrington, New Light on Washington's Fort Necessity (Richmond, Va.: Eastern National Park and Monument Assoc., 1957), pp. 38-42; James R. Hinds and Edmund Fitzgerald, "Fortifications in the Field and on the Frontier," Periodical Vol. IX, No. 1 (Spring 1977), pp. 48-49.

21David A. Simmons, The Forts of Anthony Wayne (Fort Wayne, Ind: Historic Fort Wayne, 1977), pp. 10-11.

22Anthony Wayne to David Strong, May 29, 1793, Wayne Papers, Historical Society of Pennsylvania, Vo. 26, p. 124; "General Orders for the Volunteers," September 4, 1794, Wayne Papers, Presbyterian Historical Society, Philadelphia; Dwight L. Smith, ed., From Greene Ville to Fallen Timbers: A Journal of the Wayne Campaign, July 28 - September 14, 1794, Indiana Historical Society Publication, Vol. 16, No. 3 (1952), p. 250; Entry for September 18, 1794, Diary, Jonathon Taylor Papers, Filson Club, Louisville, Ky.

23Simmons, Forts of Wayne, pp. 15-18; Interview, Ronald Burdick, Defiance College, Defiance, Ohio.

24Charles M. Stotz, "The Reconstruction of Fort Ligonier: The Anatomy of a Frontier Fort," Bulletin of the Association for Preservation Technology, Vol. VI, No. 4(1974), p. 63; Robinson, American Forts, p. 41.

25Simmons, Forts of Wayne, pp. 19, 26.

26Civil War era drawing is an excellent resource showing this type of activity. David H. Donald, ed., Gone for a Soldier: The Civil War Memoirs of Private Alfred Bellard, (Boston: Little, Brown & Co., 1975), p. 164; Meigs, "Notes on Field Fortification."

27H. Mahan, A Complete Treatise on Field Fortification (New York: Wiley and Long, 1836), pp. 53-60.

28Heitman, Historical Register and Dictionary of the United States Army. (Washington, D.C.: Government Printing Office, 1903), Vol. 1, 417; David A. Simmons, "Fort Hamilton, 1791-1797; Its Life and Architecture" (M.A. Thesis, Miami University, 1975), pp. 3, 14.

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Last Updated: 23-Mar-2011