The Defenses of Washington

References in C&O Canal Companion:
Historical Sketch pages 26-40,
Miles 1 and 4.2

The cannon depicted in this illustration belonged to Battery Martin Scott,
located 50 feet above and 200 feet from Chain Bridge.

Illustration courtesy Washingtoniana Collection,
Martin Luther King Public Library, District of Columbia.



No. 18. Washington, September 30, 1861.

* * * * * * *
XI. The works in the vicinity of Washington are named as follows:
The work south of Hunting Creek, Fort Lyon.
That on Shooter?s Hill Fort Ellsworth.
That to the left of the Seminary, Fort Worth.
That in front of Blenker?s brigade, Fort Blenker.
That in front of Lee?s house, Fort Ward.
That near the mouth of Four Mile Creek, Fort Scott.
That on Richardson?s Hill, Fort Richardson.
That now known as Fort Albany, Fort Albany.
That near the end of Long Bridge, Fort Runyon.
The work next on the right of Fort Albany, Fort Craig.
The next on the right of Fort Craig, Fort Tillinghast.
The next on the right of Fort Tillinghast, Fort Ramsay.
The work next on the right of Fort Ramsay, Fort Woodbury.
That next on the right of Fort Woodbury, Fort De Kalb.
The work in rear of Fort Corcoran and near canal, Fort Haggerty.
That now known as Fort Corcoran, Fort Corcoran.
That to the north of Fort Corcoran, Fort Bennett.
That south of Chain Bridge, on height, Fort Ethan Allen.
That near the Chain Bridge, on Leesburg road, Fort Marcy.
That on the cliff north of Chain Bridge, Battery Martin Scott.
That on height near reservoir, Battery Vermont.
That near Georgetown, Battery Cameron.
That on the left of Tennallytown, Fort Gaines.
That at Tennallytown, Fort Pennsylvania.
That at Emory?s Chapel, Fort Massachusetts.
That near camp of Second Rhode Island Regiment, Fort Slocum.
That on Prospect Hill, near Bladensburg, Fort Lincoln.
That next on the left of Fort Lincoln, Fort Saratoga.
That next on the left of Fort Saratoga, Fort Bunker Hill.
That on the right of General Sickles? camp, Fort Stanton.
That on the right of Fort Stanton, Fort Carroll.
That on the left towards Bladensburg, Fort Greble.

By command of Major-General McClellan:
S. WILLIAMS, Assistant Adjutant- General



The defenses of Washington during the Civil War included an
array of forts protecting the Virginia side of the Alexandria Aqueduct.
(Library of Congress, Geography and Maps)

Despite the switch to truss construction, maps continued to refer to the location
as "Chain Bridge," as shown on this Union map of the defenses of Washington.
Note Forts Marcy and Ethan Allen on the Virginia side--
both spots are still preserved as small parks.



Washington, D. C., December 10, 1861.

General J. G. TOTTEN, Chief of Engineers, etc.:

SIR: The resolution of the House of Representatives of July 8, of which the following is the tenor?

Resolved, That tlie Secretary of War be requested to furnish this House, as soon as practicable, plans and estimates, to be prepared by the Engineer Departmeut, for completing the defensive works on the south side of the Potomac, near this city; and also to report upon the expediency of constructing similar works of defense on the northern side of this city, with estimates for the same, so as to reduce to a minimum the number of troops required for the protection and defense of the capital?

having been submitted to me in July last, I now make the following statement:

At the time when the resolution was referred to me I was attached to the headquarters of Brigadier-General McDowell as chief engineer, and a few days thereafter I was in the field engaged in the campaign of Bull Run. Previons to this movement the army of Washington, yet weak in numbers and imperfectly organized, under General Mansfield, had crossed the Potomac and occupied the south bank from opposite Georgetown to Alexandria.

The first operations of field engineering were, necessarily, the securing of our debouches to the other shore and establishing of a strong point to strengthen our hold of Alexandria. The works required for these limited objects (though being really little towards constructing a defensive line) were nevertheless, considering the small number of troops available, arduous undertakings. Fort Corcoran, with its auxiliary works, Forts Bennett and Haggerty, and the block-houses and infantry parapets around the head of the Aqueduct, Forts Runyon, Jackson, and Albany (covering our debouches from the Long Bridge), and Fort Ellsworth, on Shooter's Hill Alexandria were mostly works of large dimensions.During the seven weeks which elapsed between the crossing of the Potomac and the advance of General McDowell's army the engineer officers under my command were so exclusively occupied with these works (all of which were nearly completed at the latter date), as to make impracticable the more general reconnaissances and studies necessary for locating a line of defensive works around the city and preparing plans and estimates of the same.

The works just mentioned on the south of the Potomac, necessary for the operations of an army on that shore, were far from constituting a defensive system which would enable an iuferior force to hold the long line from Alexandria to Georgetown or even to secure the heights of Arlington.

On the reti eat of our army such was our situation. Upon an inferior and demoralized force, in presence of a victorious and superior enemy, was imposed the duty of holding this line and defending the city of Washington against attacks from colnmns of the enemy who might cross the Potomac (as was then deemed probable) above or below.

Undecided before as to the necessity, or at least the policy, of sur- rounding Washington by a chain of fortifications, the situation left no longer room to doubt. With our army too demoralized and too weak in numbers to act effectually in the open field against the invading enemy, nothing but the protection of defensive works could give any degree of security. Indeed, it is probable that we owe our exemption from the real disaster which might have flowed from the defeat of Bull Run?the loss to the enemy of the real fruits of his victory?to the works previously built (already mentioned), and an exaggerated idea on his part of their efficiency as a defensive line.

The situation was such as to admit of no elaborate plans nor previously-prepared estimates. Defensive arrangements were improvised and works commenced as speedily as possible where most needed. A belt of woods was felled through the forest in front of Arlington and half-sunk batteries prepared along the ridge in front of Fort Corcoran and at suitable points imear Fort Albany, and a battery of two rifled 42-pounders (Battery Cameron) was established on the heights near the distributing reservoir above Georgetown to sweep the approaches to Fort Corcoran.

Simultaneously a chain of lunettes (Forts De Kalb, Woodhury, Cass, Tillinghast, and Craig) was commenced, connecting Fort Corcoran and the Potomac on the right with Fort Albany on the left, and forming a continuous defensive line in advance of the heights of Arlington. The wooded ridge which lies north of and parallel to the lower course of Four Mile Run offered a position from which the city, the Long Bridge, and the plateau in advance of it could be overlooked and cannonaded. While our external line was so incomplete, it was important to exclnde the enemy from its possession. Access to it was made (lifficult by fell- ing the forest which covered it (about 200 acres), and the large lunette (Fort Scott) was commenced as soon as the site could be fixed (about the middle of August). The subsequent establishment of our defensive line in advance throws this work into the same category with Forts Corcoran, Albany, Runyon, &c., as an interior work, or second line, but it is nevertheless an important work, as, taken in connection with Forts Richardson, Craig, &c., it completes a defensive line for Washington independent of the extension to Alexandria.

The defense of Alexandria and its connection with that of Washington was a subject of anxious study. The exigency demanding immediate measures, the first idea was naturally to make use of Fort Ells- worth as one point of our line, and to connect it with Fort Scott by an intermediate work on Mount Ida. An extended study of the topography for several miles in advance showed that such a line would be almost indefensible. Not only would the works themselves be commanded by surrounding heights, but the troops which should support them would be restricted to a narrow space, in which they would be overlooked aud harassed by the enemy?s distant fire. The occupation of the heights a mile in advance of Fort Ellsworth, upon which the Episcopal Seminary is situated, seemed absolutely necessary. The topography proved ad- mirably adapted to the formation of such a line, and Forts Worth and Ward were commenced about the 1st of September, and the line continued simultaneously by Forts Blenker and Richardson to connect with Forts Albany and Craig. Somewhat later the work intermediate between Blenker and Richardson?filling up the gap and having an important bearing upon the approaches to Forts Ward and Blenker and the valley of Four Mile Run?was commenced.

The heights south of Hunting Creek, overlooking Alexandria and commanding Fort Ellsworth, had been always a subject of anxiety. The securing to our own possession the Seminary Heights, which commanded them, diminished materially the danger. As soon, however, as a sufficient force could be detached to occupy those heights and protect the construction of the work it was undertaken, and the large work (Fort Lyon) laid out and commenced about the middle of September.

Previous to the movement of the army defensive measures had been taken at the Chain Bridge, consisting of a barricade (bullet proof and so arranged as to be thrown down at will) across the bridge, immediately over the first pier from the Virginia side, with a movable staircase to the flats below, by which the defenders could retreat, leaving the bridge open to the fire of a battery of two field guns immediately at its Maryland end, and a battery on the bluff above (Battery Martin Scott) of one 8-inch sea-coast howitzer and two 32-pounders. As even this last battery was commanded by heights on the Virginia side, it was deemed proper, after the return of the army, to erect another battery (Battery Vermont) at a higher point, which should command the Virginia Heights and at the same time sweep the approaches of the euemy along the Maryland shore of the Potomac.

During the months of May and June the country between the Potomac and the Anacostia had been examined mainly with the view of obtaining knowledge of the roads and defensive character of the grdnnd, not in reference to locating field defenses. At the period now in ques- tion there was apprehension that the enemy might cross the Potomac and attack on this side. Of course what could be done to meet the emergency could only be done without that deliberate study by which a complete defensive line would best be established. The first directions given to our labors were to secure the roads, not merely as the beaten highways of travel from the country to the city, but also as in general occupying the best ground for an enemy?s approach.

Thus the sites of Forts Pennsylvania, Massachusetts, Slocum, Totten, Bunker Hill, Saratoga, and Lincoln were rapidly chosen, and works commenced simultaneously at the first, second, third, and sixth of these points early in August. The others were taken np as speedily as the clearing of the woods an(l the means at our disposal would admit, and the gaps in the line afterwards partially filled up by construction of Fort Gaines, Forts Dc iRussy, Slemmer, and Thayer. The works men- tioneci are at this date essentially completed and armed, though there is still considerable to do in auxiliary arrangements. Our first ideas as to defensive works beyond the Anacostia contemplated only the fortification of the debouches from the bridges (Navy-Yard Bridge and Benning?s Bridge), and the occupation of the heights overlooking the Navy-Yard Bridge. With that object Fort Stanton was commenced early in September. A further examination of the remarkable ridge between the Anacostia and Oxen Run showed clearly that, to protect the navy-yard and arsenal from bombardment, it was necessary to occupy an extent of 6 miles from Berry?s place (Fort Greble) to the intersection of the road from Benning?s Bridge (Fort Meigs).

Forts Greble and Carroll were commenced in the latter part of September, and Fort Mahan, near Benning?s Bridge, about the same time. Forts Greble and Stanton are completed and armed; Forts Mahan and Carroll very nearly so. To fill up intervals or to sweep ravines not seen by the principal works, Forts Meigs, Dupont, Davis, Baker, Good Hope, Battery Iticketts, and Fort Snyder have been commenced, and it is hoped may be so far advanced before the winter sets in as to get them into a defensible condition. The occupation of the Virginia shore at the Chain Bridge was essential to the operations of onr army in Virginia. It was only delayed until our force was sufficient to authorize it. General Smith?s division crossed the bridge September ?, and Forts Ethan Allen and Marcy were immediately commenced and speedily finished.

A few weeks later (September 28) the positions of Upton?s and Munson?s Hills and Taylor?s Tavern were occupied and Fort Ramsay commenced on Upton?s Hill. The enemy?s works on Munson?s and the adjacent hill were strengthened and a lunette built near Taylor?s Tavern.

Comprised in the foregoing categories there are twenty-three field forts south of the Potomac, fourteen field forts and three batteries between the Potomac and Anacostia, and eleven field forts beyond the Anacostia, making forty-eight field forts in all. These vary in size from Forts Runyon, Lyon, and Marcy, of which the perimeters are 1,500, 937, and 736 yards, down to Forts Bennett, Haggerty, and Saratoga, &c., with perimeters of 146, 128, and 154 yards. The greater portion of them are inclosed works of earth, though many?as Forts Craig, Tillinghast, Scott, &c south of the Potomac, and Forts Saratoga, Gaiues, &c., on the north?are lunettes with stockaded gorges. The armament is mainly made up of 24 and 32 pounders on sea-coast carriages, with a limited proportion of 24-pounder siege guns, rifled Par- rott guns, and guns on field carriages of lighter caliber. The larger of the works are flanked, but the greater number are not, the sites and dimensions not permitting. Magazines are provided for one hundred rounds of ammunition, and many of the works have a considerable extent of bomb-proof shelter, as Forts Lyon, Worth, and Ward, in the bomb-proofs of which probably one-third of the garrison might comfortably sleep and nearly all take temporary shelter. In nearly all the works there are either bomb-proofs like the above, or log barracks, or block-houses of some kind.

It would be impossible to go into any details about these constructtions. I am in hopes ultimately to be able to deposit in the Engineer Office drawings of each work with sufficient detail for most purposes. The accompanying sheets, Nos. 1 and 2, will exhibit the general location and bearings of the works.[To appear in Atlas] The tabular statement herewith will show the perimeters, number of guns, amount of garrison, &c. [No tabular statement found as an inclosure to this report, but see Barnard and Barry to Williams, October 24, pp. 626-628]

It should be observed that most of the works south of the Potomac, having been thrown up almost in the face of the enemy, have very light profiles, the object having been to get cover and a defensive work as sl)eedily as possible. The couuterscarps of all the works, with few ex ceptions, are surrounded by abatis.

It is impossible, at present, to indicate the exact extent of forest cut down. (The drawings herewith represent the forest as it existed before the works were commenced.) [Omitted.] The woods in advance of Forts Worth, Ward, and Blenker have been felled; all surrounding and between the next work on the right and Fort Richardson; all the wood on the ridge on which is Fort Scott?a square mile probably?in advance of and surrounding Forts Craig, Tillinghast, and Woodbury, besides large areas north of the Potomac, &c. This fallen timber (most of which still lies on the ground,) rendered an enemy?s approach to the lines difficult. The sites of Forts Totten, Slocum, Bunker Hill, Meigs, Stanton, and others were entirely wooded, which, in conjunction with the broken character of the ground, has made the selection of sites frequently very embarrassing and the labor of preparing them very great.

The only case in which forts are connected by earthworks is that of Forts Woodbury and De Kalb, between which an infantry parapet is thrown up, with emplacements for field guns. The construction here was suggested by the fact that this was on one of the most practicable and probable routes of approach for the enemy. Infantry trenches have, however, been constructed around or in advance of other works, either to cover the construction (as at Fort Lyon), or to see ground not seen by the work (as at Forts Totten, Lincoln, Mahan, &c.).

The works I have now described do not constitute a complete defensive system.

We have been obliged to neglect much and even to throw out of consideration important matters. We have been too much hurried to devise a perfect systemn, and even now are unable to say precisely what and how many additional points should be occupied and what auxiliary arrangements should be made.

It is safe to say that at least two additional works are required to connect Fort Ethan Allen with Fort De Kalb. The necessity of protecting the Chain Bridge compelled us to throw the left of our northern line several miles in advance of its natural position, as indicated by the topography to the sites of Forts Ripley, Alexander, and Franklin. Between these and Forts Gaines or Pennsylvania one or two intervening works are necessary.

Between Forts Pennsylvania and De Russy at least one additional work is necessary.

Fort Massachusetts is entirely too small for its important position. Auxiliary works are necessary in connection with it.

Small tetes-de-pont are required around the heads of Benning?s and the Navy-Yard Bridges.

Between Forts Mahan and Meigs one or more intervening works and between Forts Du Pont and Davis another work of some magnitude are required, the ground along this line not being yet sufficiently known. A glance at the map will show it to be almost a continuous forest. It is not deemed necessary to connect the works by a continuous line of parapet, but the intervening woods should be abatised and open ground traversed by a line of artificial abatis, and infantry parapets, half-sunk batteries, &c., placed so as to protect these obstructions and to see all the irregularities of the ground not now seen from the works. Considerable work is also required in the way of roads, the amount of which I cannot state with any precision. Several miles of roads have actually been made. The works themselves would be very much strengthened by caponieres in the ditches, additional internal block-houses, or defensive barracks, &c.

The aggregate perimeter of all the works is about 15,500 yards, or nearly 9 miles, including the stockaded gorges, which, however, form a small proportion of the whole, requiring, computed according to the rule adopted for the lines of Torres Vedras, 22,674 men (about) for, garrisons.

The number of guns, most of which are actually mounted, is about four hundred and eighty, requiring about 7,200 men to furnish three reliefs of gunners. The permanent garrisons need consist of only these gunners, and even in case of attack it will seldom be necessary to keep full garrisons in all the works.

The total garrisons for all the works (one hundred and fifty-two in number) of the lines of Torres Vedras amounted to 34,125 men; and as the total perimeters are nearly proportional to the total garrisons, it appears that the lines about Washington involve a magnitude of work of about two-thirds of that in the three lines of Torres Vedras.

The works themselves, fewer in number, are generally much larger than those of Torres Vedras, and involve, I believe, when the amount of bomb-proof shelter in ours is considered, more labor per yard of perimeter; but the latter lines involved a greater amount of auxiliary work, such as the scraping of mountain slopes, palisading, abatis, roads, &c., than we have had occasion to make.

The lines of Torres Vedras were armed with five hundred and thirty-four pieces of ordnance (12,9, or 6 pounders, with a few field howitzers); ours with four hundred and eighty pieces, of which the greater number are 32-pounders on barbette carriages, the rest being 24-pounders on the same carriages, 24-pounder siege guns, 10, 20, and 30 pounder rifled guns (Parrott), with a few field pieces and howitzers. As to number of guns, therefore, our armament approaches to equality with that of the famous lines mentioned; in weight of metal more than doubles it.

The above applies to our works as now nearly completed, and has no reference to the additional works I have elsewhere mentioned as hereafter necessary. It is impossible to give any other statement of actual cost of the works than the total amount expended thus far. The work has been done partly by troops and partly by hired laborers, the works north of the Potomac being mostly done by the latter. The large amount of carpentry in magazine frames and doors and blindages, bar- rier gates, stockades, block-houses, defensive barracks, &c., has kept a large gang of carpenters all the time at work, and caused a large expenditure for lumber. The entire amount umade available by the Department for these works has been $344,053.46, and this will all have been expended (or more) by the end of the present month. This would give an average of a little over $7,000 for each of the forty-eight works; but of course the real cost of them, has been very unequal.

The importance of perfect security to the capital of the United States in the present state of affairs can scarcely be overestimated, and these works give a security which mere numbers cannot give, and at not a tithe the expense of defense by troops alone.

It is impossible to make anything like a reliable estimate of what additional amount of funds will be required. In a letter to the General-in-Chief commanding Army of the Potomac, of December 6, I urged an immediate appropriation of $150,000, and this appropriation has been asked for of Congress by the Secretary of War.

Should the auxiliary works which I have suggested be undertaken and the scarps be revetted, I believe a larger sum than this may be judiciously expended. I therefore recommeud that an additional $100,000, or $250,000 in all, be provided for the continuation and completion of the defenses of Washingtou. These works acquire new importance if the probability of a foreign war is taken into consideration. In view of this new importance, of the semi-permanent or possibly permanent necessity for such works, it is proper to suggest that early in the spring the scarps be protected by a timber or thin brick revetment, and the exterior and other slopes, where not already done, be sodded, and that wooden caponieres, or counterscarp galleries, be arranged to flank all unflanked ditches?at least of important works. The strengthening of the profiles where necessary has already been mentioned as important.

It remains with me to express my sense of the zeal and efficiency with which the officers of engineers serving with me since April have discharged their duties. To their energy and skill I am mainly indebted for the successful accomplishment of this really great work, and I feel that I have a right to say that for the safety of the capital in the hour of its greatest danger; for saving the cause of established government and the Constitution from the most serious blow the rebels could have inflicted, the country owes much to the labors of the engineers. From their great experience and cunstant association with me since April the services of Colonels Woodbury and Alexander have been particularly important in the laborious recounaissances and in directing the execution of extensive lines of works.

General Wright laid out and superintended the construction of Fort Ellsworth, and General Newton, who since the 1st of September until recently had charge of the works below Four Mile Run, laid out and directed the construction of Fort Lyon.

Captains Blunt and Prime, Lieutenants Comstock, Houston, McAlester, Robert, Paine, Cross, Babcock, and Dutton have served with efficiency during the whole or part of these constructions, and the lamented Snyder lost his life from over-zealousness in (lischarge of his duties while in impaired health from his services at Charleston Harbor and Fort Sumter. Since the relief of Captain Prime, Lient. H. L. Abbot, of the Topographical Engineers, has taken his place, proved himself a most energetic amid valuable assistant, having completed Fort Scott and built Forts Richardson and Barnard. In carrying out so many works at the same time, and for organizing and managing the large bodies of hired laborers employed, it has been found necessary to call in the aid of civil engineers, not omily because the engineer officers were too few to keep proper supervision, but because a large portion of those under my orders have been called off to other duties, such as the organization of bridge trains, the instruction of emigineer troops, &c. Civil Engineers Gunnel, Frost, Faber, Childs, and Stone have rendered valuable serv- ices; also Mr. (now major of the Fifteenth New York Volunteer Regiment) Magruder. I should also express my warmest acknowledgment to Mr. James Eveletli, of your office, who, as disbursing agent and pay-master of the large bodies of hired laborers, has performed an amount of duty I should hardly have expected from one individual. I could wish that the law under which he serves the Engineer Department, might be so modified in his case as to enable him to receive some adequate compensation for the extra duties he has voluntarily assumed. I should have mentioned, in connection with my statement of the amount actually expended, that the Tieasury Department has advanced over $20,000 on account of the defenses of Washington, which should he refunded. I feel it my duty in this place to urge that Congress should take immediate measures to assess the land and other damages arising from these works and from the occupation of troops. In most cases the owners are ill able to bear temporarily the losses to which they have l)een subjected.

In conclusion, I would add that to the great importance attached to these works by the commanding general (now Commander-in-Chief), to his valuable suggestions and prompt and cordial co-operation, the present state of efficiency of the defenses of Washington is in no small degree due.

I am, very respectfully, your obedient servant,

Maj. of Eng., Brig. Gen., and Chief Eng. Army of Potomac.



  • The General Orders first naming the forts is found in Series 1, Volume 5 (Page 611) of The war of the rebellion: a compilation of the official records of the Union and Confederate armies. [The original page images of the Official Records, as printed by the Government Printing Office beginning in 1881, can be viewed at the Cornell University site, Making of America.]
  • General Barnard's December 1861 report is found on pages 678-685, Series 1 - Volume 5, of the Official Records.
  • Details of defense works at Rosslyn and Chain Bridge are from The Atlas to Accompany the Official Records, Government Printing Office, 1891-1895, Plate LXXXIX, Defenses of Washington, Extract of a Military Map of N.E. Virginia, by the Engineer Bureau, War Department, to accompany the October 30, 1865 report of Richard Delafield, Chief of Engineers, to the Secretary of War. [Originals in the Geography and Map Division, Library of Congress--the Atlas was reprinted in 1983 by the Arno Press, Inc.]

Also on the Web:



| Home | C&O Canal | Historical Sketch | Falls Region | Piedmont and the Sugar Lands | Blue Ridge & Great Valley | The Endless Mountains |