A look at the sources of the McDowell Map

I mention the McDowell map a lot.  To me it is a “primary source” of great value.  The map depicts the topography, roads, and places of Northern Virginia in fine detail.  It is also the worksheet over which Federal officers planned operations.  If they needed to move from the ubiquitous “Point A” to “Point B” then it was this map which depicted the relation of the two points, and the road structure between.

To the left side of the map, and unfortunately blocking some of Fauquier County, is a section of text which I have been snipping around to create the maps used of late.  It is titled “Data used in compilation.”


Let me attempt a transcription of this so you don’t have to break out the glasses:

Surveys – by John J. Young, Wm. H. Paine and others under the direction of Top. Engineers over that portion of Virginia included between the river Potomac and a line from Chain Bridge, via Minor’s Hill, Peach Grove, Vienna, Fairfax C.H., Annandale, Springfield Station, and Accotink to Mount Vernon, also along the turnpike from Prospect Hill to Drainsville [sic].

Surveys – by Capt. Preston C.F. West Vol. T.E. Smith’s Division & by Coast Survey parties under direction of Lieut. Col. Macomb T.E., A.D.C. Leesburg Turnpike from Falls Ch. to Sugerland Run, also Georgetown Turnpike from Prospect Hill to Chain Bridge and Country between it and Potomac.  Comparisons have been made with such other Coast Survey Charts as could be obtained especially with that furnished by Genl. Franklin of the Country occupied by his Division.

Reconnaissances – by Lt. Col. Macomb, Top. Eng. beyond Drainesville [sic] by Maj. Palmer, T.E. to Mathias Point, White House point and to Flint Hill by Capt. Williamson opposite Quantico Creek, by 1st Lt. Abbot, T.E. about Blackburns Ford and Vicinity, by Capt. Schumacher, V.T.E. to Genl. King’s Brig. of his outposts by Capt. Wm. Heine, V.T.E. to Genl. Heintzelman’s Div. of Country about Bone Mill and toward Wolf Run shoals by Top. Engineers and other U.S. officers to Centreville and Sudley Springs.

Informations – furnished by Genl. McCall, Gen. Meade, and Gen. Reynolds in vicinity of Drainesville [sic] and Difficult Cr. and between turnpike and the Potomac.

Informations – furnished from Gen. Hancock, Gen. Brannan, and Capt. West Vol. T.E. of Country occupied by Smith’s Division.

Informations – furnished by General Morell and General Butterfield of Country occupied by Gen. Fitz John Porter’s Division.

Informations – furnished by officers attached to Gen. Wadsworth’s, Gen. King’s, and Gen. Augur’s Brigades.

Informations – furnished by Maj. Forstner, Vol. T.E. to Gen. Blenker’s Division.

Informations – furnished by Gen. Franklin.

Informations – from Gen. Hooker of country occupied by his div, – also from Col. Ch. Scranton & Mess W.H. Scranton, Hiles, Hornbucker, Burd, Gaston, Arnhast, Gregg, Dills, Athey.

Informations – obtained by Gen. Richardson and Capt. Wm. Heine, Vol. T.E. to Gen. Heintzelman’s Division beyond outposts and towards the Occoquan.

Informations – given by Mr. Roberts  & furnished by Gen. Kearney, Country about the Occoquan, etc.

Informations – given by Lt. Col. Alexander Engs. U.S.A. & Mr. Hawshurst, County about Fryingpan etc.

Map – N.E part of Dist. of Columbia by A. Boschke.

Map – State of Virginia by Herrman Boye, corrected 1859 by L. V. Buchholtz.

Map – furnished by Bureau T.E. Survey for Great Falls Aqueduct by Lieut. M.C. Meigs Corps of Engineers, 1852.

Map – Mt. Vernon estate by Wm. Gillingham.

Map – Loudoun County by Yardley Taylor.

Map – Orange and Alexandria Railway, by August Faul.

Manuscript – N.E. part of Virginia by the Bureau of Topographical Engineers.

Manuscript – Accotink Turnpike by Gen. Geo. Washington.

Manuscript – Loudoun & Hampshire Railway 1854.

Manuscript – Manassas Gap independent Line of Railway 1853.

Manuscript – Projected Canal between Goose Creek and Alexandria by Baldwin.

Additions & Corrections – for Rappahannock and Rapid Ann [sic] Rivers and their vicinity furnished from the Records in Office of Lt. Col. J.N. Macomb, A.D. Camp and Ch. Top. Eng. Army of Potomac.

The list of sources is like a “who’s who” of the Army of the Potomac.  Too many names for me to tag for this post.

And George Washington!  That tells us something about the detail and accuracy of the work done by our first president.  It also tells us how inclusive the scope set by the officers compiling the information shown on the map.

Marching Through Loudoun: June 20, 1863

At 4 a.m. on this day (June 20) in 1863, General Henry Slocum forwarded a report to the headquarters of the Army of the Potomac. The content in the message was, for the most part, just a repeat of the previous day’s correspondence – need a bridge at Edwards Ferry, redoubts cover that crossing point, and the execution. But the filed copy, which was later transcribed into the Official Records, included the annotation “Received, War Department, 8 a.m.” Normally, this might not seem significant. However, as mentioned yesterday, message traffic from Leesburg relayed to Poolesville. From there the message went by telegraph to the centralized telegraph station in the War Department Building in Washington. From there the message was relayed again by telegraph to Army headquarters at Fairfax Courthouse. Not only did these transfers take time, it also meant in some cases authorities in Washington had access to information before Major-General Joseph Hooker received it.

On the evening of June 19, a heavy thunderstorm rolled through. By some accounts rains continued off and on until the 21st. In Loudoun Valley, the cavalry forces rested and regrouped following a hard day’s fighting. Brigadier-General Alfred Pleasonton reported the presence of Confederate infantry, but determined those were up to support his opposite number, Major-General J.E.B. Stuart. Pleasonton added, “I have been attacking Stuart to make him keep his people together, so that they cannot scout and find out anything about our forces…Lee is playing his old game of covering the gaps and moving his forces up the Shenandoah Valley.” A bit of advice often given in regards to scouting operations – if you cannot find the enemy, at least make sure the enemy does not find you – might apply here for Pleasonton. (And might we ask if information denied Stuart, and thus General Robert E. Lee, played into decisions on the Confederate side.)

Late in the afternoon, Hooker sent orders to Pleasonton authorizing the cavalry to press the Confederate cavalry on the 21st. Hooker also directed two brigades from the Fifth Corps, at Aldie, to support the cavalry. “The commanding general is very anxious that you should ascertain, at the earliest possible moment, where the main body of the enemy’s infantry are to be found at the present time, especially A.P. Hill’s corps.” Thus set in motion events leading to the fourth major cavalry battle of the campaign.

In other cavalry operations, Major-General Daniel Butterfield, Chief of Staff, called for another set of patrols by Major-General Julius Stahel’s cavalry. “…a force of cavalry, to go, via Manassas, Bristoe, Catlett’s, and Dumfries, returning by Wolf Run Shoals; another, via Brentsville, Howison’s Ford, and Greenwood, returning by Wolf Run Shoals. Five hundred men in all will answer the purpose…” Again, these troopers were not, at that time, part of the Army of the Potomac. And of course those places were well outside my “study area” of Loudoun. But those troopers soon would be part of the Army and be marching through Loudoun. Furthermore, the Army leaned on Stahel at this time due to an overall shortage of cavalry for the required missions. Pleasonton’s divisions had to concentrate for what amounted to a covering force battle in Loudoun Valley. That left Stahel as the only force for scouting in other directions.

In addition to Stahel, other troops from the Washington Defenses – Major-General Samuel Heintzelman’s command – operated across the Army of the Potomac’s sector. I’ll refer to those as part of the Twenty-second Corps on the map and depict them in green.


In Centreville was a 7,262 man division under Brigadier-General John Abercrombie. Many of those troops were counting the last days of their enlistments. But two of these brigades, along with two artillery batteries, would join the Army of the Potomac within days (including a fresh brigade of Vermonters, posted at the time in vicinity of Wolf Run Shoals). Another division, consisting of the Pennsylvania Reserves under Brigadier-General Samuel Crawford, posted brigades at Upton’s Hill, Fairfax Station, and Vienna. My pal Ron Baumgarten has covered their garrison life in detail over a series of posts recently. The Reserves would also soon join the Army of the Potomac. One other force of note was a brigade of 2,000 infantry posted at Poolesville, Maryland.

June 20th saw limited movement among the infantry corps of the Army. Brigadier-General Albion Howe’s division of the Sixth Corps marched to Bristoe Station (again, off my map above) to guard the left flank. Second Corps continued its march to Thoroughfare Gap, with one division left back at Gainesville.

What I consider the most significant activity of the 20th came at 5:20 p.m. Butterfield sent orders to Captain Charlest Turnbull:

Lay one bridge at Edwards Ferry. Upon receipt of this, communicate to General Slocum, at Leesburg, your orders. Having laid one bridge, send boats and force enough for bridging Goose Creek, near Leesburg and Alexandria pike, say 75 feet wide.

However, Turnbull had a problem. He arrived at Edwards Ferry with 1,200 feet of bridging and 60 pontoon boats. He estimated the river at 1,400 feet wide, and it was rising due to the rains.

Earlier in the day Major Ira Spaulding related to Brigadier-General Henry Benham that the detachment at Edwards Ferry needed more bridging. At around 9 a.m. he requested “fifteen boats, completely furnished; also about 50 extra chesses, and some extra lashings in coils, uncut.” Spaulding then started for Washington, presumably to sort out equipment and forward what was needed. Anticipating that equipment would arrive by morning, Turnbull affirmed to Butterfield, “Will go ahead and do the best I can.”

At the close of June 20, the Army of the Potomac had firmly established the Bull Run-Catoctin line with the Second Corps at Thoroughfare Gap; Fifth Corps at Aldie; and Twelfth Corps at Leesburg. Three more infantry corps were just a short march away in reserve. And the cavalry corps was looking for Lee’s main body … in the wrong place, but at least they were looking. But the engineers were about to put in place a resource which, once the Confederate main body was found, allow the Army of the Potomac to pivot again in pursuit.

(Citations from OR, Series I, Volume 27, Part III, Serial 45, pages 223-29.)