Notes on Latrobe and the Marble Quarry

Reference in C&O Canal Companion: Mile 38

Above: Latrobe's sketch of the wharf landing and crane below the U.S. Capitol
gives an idea of how the columns were transported via boat from the Potomac quarry.
(dated May 1, 1817, Library of Congress, Prints and Photographs)

Below: This closeup of one of the marble columns in Statuary Hall shows the
unusual patterns that so captivated Latrobe. (Photo by M. High)


Latrobe's 1815 letter dexcribing the Potomac breccia ...


Capitol Augt. 8th. 1815


I returned yesterday from my visit to the Limestone and Marble country in Frederic and Loudon Counties, and now beg leave to report to you the results.

There is on the S. East of the Cotocktin Mountain a very large extent of country, which abounds in immense Rocks of Marble, or Limestone Breccia, that is of a Stone consisting of fragments of ancient Rocks bound together by a calcareous cement, and thus becoming one solid and uniform (homogenous) Mass of Marble. This Range of Rocks I have traced from James River to the Delaware, but it appears nowhere of a more beautiful kind than on the Patowmac. A specimen will be submitted to you as soon as I can get it polished.

The largest Mass of this Kind of Rock is situated on the Maryland side of the Patowmac on land the property of Samuel Clapham Esqr. It overhangs the River, and would furnish without any land carriage all the Columns of the Capitol of one block each if required, and of beauty not exceeded in any modern or ancient building. It is impossible for me at this moment to say more, than that it is practicable to obtain all our Columns there, but at what price of material or Labor, must be determined by further investigation.


Whether the compound Marble is used for building or not, it will however furnish an inexhaustible source of excellent lime.

The Rock I have mentioned belonging to Samuel Clapham Esqr. is situated most conveniently for the erection of Kilns, close to the river, of any place that I have seen. The same Stone is found on both sides of Potowmac plentifully for 12 to 14 miles above Mr. Clapham's, and on the Virginia side for 2 or 3 miles below. The estate of the late Roger Nelson is conveniently situated for a supply, but his death and the time necessary for the settlement of his affairs, prevent any offer however from them at present. From Carolton manor nothing is to be expected. Below Mr. Clapham's the proprietors are unable for want of capital to erect the necessary Kilns. This being the result of my enquiries, I entered into a preliminary negotiation with Mr. Clapham, and went so far, as to ascertain, that he will contract to deliver at Georgetown, or if conveniently it can be done, in the Tiber 10,000 Bushels of Lime at 60 cents per bushel should the Commissioners on their part be willing to enter into a contract for that or a larger quantity. But he will not incur the expense of erecting the necessary Kilns unless certain of disposing of that quantity of Lime.


Latrobe's letter to the editors
of the National Intelligencer ...

Capitol January 18th. 1817


The very beautiful block of variegated marble which is now in the lower vestibule of the south wing of the Capitol, and is a part of the pilaster of the House of Representatives, has occasioned so many inquiries, that I beg you to insert the following account of it, for general information.

It is now about 20 years ago, since I observed, in visiting that part of Virginia which lies immediately below the south west mountain, a Breccia or Bedding stone, scattered in large masses, as well as in small lumps, and having a range parallel to the general range of our mountains. I also observed the same Breccia on the south side of Appomattox in Virginia, and was informed that it was also common in the same range on the banks of the Roanoke.--I have only a cursory notice in my journal of its appearance in the southern parts of Virginia, with a memorandum, that some of the pebbles of which it is composed were calcareous. I had then no better test than common vinegar. A few years afterwards, the same stone occurred to me near Frederick town in Maryland, and attracted more notice, for I sent a block of it to Philadelphia. I there analysed it, with the assistance of Mr. Thomas Smith, a chemist and natural philosopher, whose untimely death at sea on his return from Europe deprived our country of one of its most valuable citizens. It proved to be composed of pebbles of various kinds of marble combined by a cement, calcareous, but less pure and mixed with alumine and silex (clay and flint). The same breccia I afterwards discovered in great quantity, and in still in the same range of country, in the neighborhood of Reading, and on trial it was found to receive an admirable polish. This was about the year 1799 or 1800.


When the Capitol of the United States was to be restored, in passing by four different routes across the mountains, to, & from the westward, I observed the same marble always in the same range of country, on both sides of the Potomac.

The public buildings had hitherto been constructed with the free stone found in the neighborhood of Aquia Creek. The same The same quarries were resorted to, for their re-establishment, but it has singularly happened, that neither in the old quarries, nor in the new ones which have been opened, stone, of a texture fit for the finer works of the buildings, has yet been discovered. Although formerly no difficulty was found in procuring stone of every quality required, for the columns of the House of Representatives, and Senate chambers particularly, no fine stone could be got. This gave an opportunity of recommending a trial of the new marble. On exploring the neighborhood of the Potomac, in Virginia and Maryland, in August 1815, I was enabled to report, that masses of any size might be procured close to the water's edge, and to bring with me many very beautiful specimens of the stone. In March, 1816, I again visited that country, and returned still more assured of the success of the attempt to bring the marble into use--and in June, 1816, a contract was made by the present Commissioner, (Col. Lane) with Mr. Hartnet, an experienced marble mason, for all the columns and pilasters of the House of Representatives: and, altho' only one polished block has as yet been delivered, great progress has been made at the quarry, in procuring all that will be required. In this undertaking, every species of difficulty has been encountered, in opening the quarry, in collecting laborers, quarriers and marble masons, in providing dwellings, shops and tools, and in organizing a great undertaking on the banks of the river where not habitation before existed.

I now proceed to give some account of the situation of this great range of marble upon the map of our country, which will be better understood by referring to the maps of Virginia, Maryland, and Pennsylvania.


The Potomac, breaking through the Cotocktin mountain, crosses the Breccia until it meets the Monocasy under the S.E. side of the valley; it then suddenly turns to the S.W. and again enters the Breccia, leaving a large mass on the Maryland side (the east side) of the river, by far the highest part of this irregular compound. It immediately however turns to the S.E. and at Conrad's Ferry leaves the Breccia finally.

On this high mass in Maryland, in which the quarry is opened, lies a deep blue stratified limestone, and, upon the limestone, a vast mass of alluvial soil. On raising the blocks of Breccia in horizontal masses of 100 to 150 tons, it is found, that it breaks indifferently through the pebble or through the cement; that many ancient fissures are solidly filled with white marble or calcareous spar, and that there is evident chrystalization or tendency to sparry chrystalization throughout the mass.

To give a list of the variety of marbles contained in this irregular stone, would fill as much paper as I have already occupied. I therefore reserve for a future communication many important facts.


P.S. It is only justice to Mr. Hartnet to add that the block of marble now at the Capitol is part of a loose fragment, long exposed to the weather, as its under surface proves. It is therefore, in its polished texture, very inferior to the blocks since quarried from the solid rock, nor would he have sent it down, had it not been done at my particular request, in order to exhibit a specimen of the marble to the members of Congress at their present session. The block is 9 feet long, 2 feet 6 inches wide, and about one foot thick, and weighs two tons. The columns 2 feet 8 inches in diameter, 22 feet long, may be easily procured in one block, and conveyed by water from the quarry to the foot of Capitol Hill.

B. H. L



  • Latrobe's letters on the Potomac breccia are included in The Correspondence & Miscellaneous Papers of Benjamin Henry Latrobe, edited by John C. Van Horne, Yale University Press, 1988. The original copy of Latrobe's letter to the commissioners is in the National Archives.
  • Detail of Latrobe drawing is taken from digital image, Library of Congress, Prints and Photographs, call number LC-USZC4-53.
  • Further evidence of the location of the quarry is found in a sketch of Latrobe's entitled "Breccia Marble Rock opposite Clapham's Island, March 14, 1816," held by the Maryland Historical Society. (Clapham's Island is present-day Mason's Island.)

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