Notes on Sideling Hill Aqueduct, Dam #6, and the Bridge at Great Cacapon

References in C&O Canal Companion:
Miles 133.7, 134.2, and 136.6

The stone railroad bridge across the Great Cacapon in the winter of 1993.
Below: Sideling Hill Aqueduct, in late spring 2001,
with Sideling Hill in the background. (Photos by M High)

Added to Mile 134 in the Updated edition:

The original plans for the Woodmont Rod & Gun Club have changed. The club is now managed by Maryland?s Department of Natural Resources in conjunction with the Izaak Walton League.

"Hunting and hiking are permitted on the 2,000-acre property. For hunting information, contact the Wildlife Heritage Division (301/478-2525). Groups may arrange for use of the stone lodge; contact the Fort Frederick State Park for more information."

Added to Mile 136.2 in the Updated edition:

"The original name, "Side Long Hill," is said to have appeared first on the famous map of the mid-Atlantic region made by Joshua Fry and Peter Jefferson in 1755. However, the name "Sidelong Hill Creek" appears as early as 1736 on the map that Winslow produced for the Fairfax survey. The Creek was chosen as the dividing line when the Maryland Assembly created Allegany County out of Washington County on December 25, 1789. (Allegany thus became the westernmost county?Garrett County was not created until after the Civil War.)"


To be added

Mile 133.7:

Intitially, the canal company had intended to place its Dam #6 just below the mouth of the Cacapon. However, by 1837 their engineers had concluded that the riverbed below the Cacapon was unsuitable as a foundation for the dam. In addition, the dam would have had to be higher to cross the river here, and thus more vulnerable to floods. Not to be deterred, the company came up with another scheme to capture the trade from the Cacapon branch -- they proposed building a dam across the mouth of the Cacapon and using it to water a short connecting canal up to Dam #6, where the boats from the Cacapon would cross the slackwater "pond" and enter the main canal. The possibility of a cross-river connection soon became moot, when the B&O Railroad extended its line along this stretch of the Potomac Valley and naturally placed one of its stations on the Cacapon.

Mile 134.2:

As the canal company put the finishing touches on Dam #6 in 1838, it began to visualize, at last, a profitable connection with coal that would be boated down from Cumberland in the fall, "when the waters of the upper Potomac admit of navigation." However, the opening of the B&O Railroad to Cumberland in 1842 brought a more practical, if perhaps less agreeable solution. ***


From Charles Fenton Mercer's December 1832
reports to the Directors of the Canal Company:

Let the next dam, No. 6, be placed at the best situation for the next feeder which is believed to be immediately below the mouth of the Great Cacapon, and 26-1/2 miles above dam No. 5 ....

From the ninth annual report to the stockholders
dated June 12, 1837:

A guard-lock at the dam serves the purposes of a feeder to the canal, and for the admission of boats navigating the pool, as well as for the reception of the trade from the Cacapon, which by a dam across the stream at its mouth, and a canal of less than one mile in length, may be connnected with the main stem by means of the pool and guard lock. By former surveys it was proposed to locate the dam a short distance below the mouth of the Cacapon; but on a more thorough examination by our engineer, he reportedly decided against the location at that point, mainly on the ground that the bed of the river did not present a suitable foundation for such a structure, and that the hazard of its being swept away would be greatly augmented by its increased height at that point. Other and substantial reasons were adduced, which decided the Board in the adoption of the present location.



Official Records, Series 1, Volume 5
Page 1018 - message from General T. J. "Stonewall" Jackson:

Unger?s Store, Morgan County, Virginia,
January 2, 1862.

Commanding Department of Northern Virginia:

MY DEAR GENERAL: Yours of the 31st ultimo is at hand, and tends to confirm information previously received by we that an advance was to be made on Winchester by forces from Reynolds and Banks. I am taking a position such as to prevent their junction without giving me an opportunity of striking a blow at one of them previously, should circumstances justify it. Tomorrow I hope to recover Bath, and before leaving Morgan I desire to drive the enemy out of this county and destroy the railroad bridge which has been recently constructed across the Big Cacapon. Reynolds? forces in and about Romney are estimated at about18,000, but I think this is too large; yet I fear that it is true. At last advices General Banks? headquarters were at Fredericktown, but he has had ample time to change them siuce.

Very truly, your friend,

[Major-General, Commanding Valley Dist?rict.]



Pages 391-392 - from report of Gen. Thomas J. Jackson,
C. S. Army, of operations from November 4, 1861, to February 21, 1862.

The next morning (January 4) the march was resumed, General Loring still in front, and continued without farther interruption until within a mile or two of the town [Bath], when General Loring, without sufficient cause, permitted the head of the column repeatedly to halt, and thus lost so much time as to make me apprehensive that unless I threw forward other troops I would have to remain out of Bath another night.
So prematurely and repeatedly had General Loring permitted the head of the column to halt, that even his skirmishers were not kent within continuous sight of the enemy. Though I followed after the cavalry and entered the town in advance of the skirmishers, yet both the enemy?s artillery and infantry were out of sight. I moved on b- wards Sir John?s Run Depot, the direction in which there was reason to believe that they had retreated, until I had advanced sufficiently far to prevent Colonel Gilham from missing the way to the depot. Immediately afterwards I returned to the road leading to the railroad bridge over the Big Cacapon River, and directed Colonel Rust to move to the bridge and destroy it. I then returned towards Bath, for the purpose of following in person the road taken by the fugitive cavalry, and which was the only remaining one by which the enemy could have escaped, and on the way directed Colonel Maney to continue scouring the hill that he was then moving upon, and afterwards to join me.
On the evening of the 4th Lieutenant-Colonel Ashby, who, in command of a detachment composed of some cavalry and an infantry force under Maj. E. F. Paxton, and a working party under Capt. H. T. Colston, had been enlarging the break in Dam No. 5, joined me at Bath. From the most reliable information received the force of the enemy at Bath was 1,500 cavalry and infantry, with two pieces of artillery. The next morning I demanded the surrender of Hancock, stating that if the demand was not acceded to the place would be cannonaded. The commanding officer refused to comply with my demand, and I cannonaded the place for a short time, and proceeded to construct a bridge for crossing the Potomac about 2 miles above the town. This work was intrusted to Col. W. A. Forbes, who commanded and progressed with it in a manner highly creditable to himself and his com- mand. Colonel Forbes was assisted in this work by Captain Briscoe, assistant quartermaster, an enterprising and valuable officer. On the 6th the enemy was re-enforced to such an extent as to induce me to believe that my object could not be accomplished without a sacrifice of life, which I felt unwilling to make, as Romney, the great object of the expedition, might require for its recovery, and especially for the capture of the troops in and near there, all the force at my disposal. The invader having been defeated and driven across the Potomac, the telegraph line broken at several points, and the railroad bridge across Big Cacapon destroyed, thus throwing material obstacles in the way not only of transmitting intelligence from Romney to Hancock, but also of receiving re-enforcements from the east, arrangements were made for moving on Romney. The next day, the 7th, the command was put in motion; Lieutenant-Colonel Ashby, with his cavalry, brought up the rear; but before leaving Alpine Depot, opposite Hancock, destroyed a large amount of public stores that had fallen into our hands and could not be removed for want of means.


  • Frontier Forts along the Potomac and its Tributaries, William H. Ansel, Jr., Springfield, West Virginia, 1984, reprinted by Fort Pearsall Press, Inc., 1995. [Ansel bases the name "Fort Dawson" on the possibility that the fort at the mouth of the Cacapon was built on land owned by Isaac Dawson, and was perhaps constructed by Dawson and his neighbors. However, I have not found the name used in the correspondence of Washington, Sharpe, or Dinwiddie, or in the proceedings of the General Assembly of Maryland.]
  • Report of Gen. Thomas J. Jackson, January 4, 1862- Skirmish at Great Cacapon Bridge, from Official Records, Series 1, Volume 5, pages 391-395.
  • "Two Reports of the President to the Directors of the Chesapeake and Ohio Canal Company on the Present State of the Finances of the Company, and an Extension of the Navigation of the Potomac to a Point Nine Miles Above the Town of Cumberland," signed by C.F. Mercer, December 15, 1832, printed by Gales and Seaton, Washington, DC, 1832.
  • "Ninth Annual Report of the president and directors of the Chesapeake and Ohio Canal Company, to the stockholders, made June 12, 1837" and "Tenth Annual Report of the president and directors of the Chesapeake and Ohio Canal Company, to the stockholders, made June 4, 1838." reprinted in Memorial of the Corporation of the City of Washington, Remonstrating Against the Surrender to the State of Maryland of the stock held by that Corporation in the Chesapeake and Ohio Canal, March 11, 1840, printed by Blair and Reeves.

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