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Monocacy Railroad Covered Bridge

Frederick MD-10-17x Monocacy River Unk 3 350' 1831 1854
Lewis Wernwag built both the Monocacy Covered Bridge on the roadway at Frederick Junction just southeast of the city of Frederick and the Monocacy Railroad Covered Bridge that carried the tracks of the Baltimore & Ohio Railroad just a quarter of a mile upstream of the roadway bridge. This bridge is considered a covered one even though the train likely crossed on the roof of the bridge. The "roof" over the trusses was made of metal and also served as a deck. The truss system was protected with weather boarding.
From Michael Caplinger's book Bridges Over Time:
Only two years after dismissing (Colonel Stephen) Long's wooden truss as unfit, the (B&O) railroad was forced by a lack of time and money to build a wooden bridge across the Monocacy River, some 20 miles east of Harper's Ferry. By this time (Lewis) Wernwag must have changed his opinion on wooden railroad bridges for he built a three-span 330 foot long bridge that marked the first use of timber on the main stem.¹
References to the length of the Monocacy Railroad Bridge varies from 330 feet as stated above in Michael Caplinger's book, to 345 feet as stated in the article shown below from the Baltimore Sun in 1854, to a detailed article in 1831 from the The Frederick Town Herald that puts the length at 317 feet from piers to abutments, 339 feet total length of arches and 350 feet for the roof length. Because of the detail provided in the 1831 article we consider the roof length of 350 as likely the easiest way to measure the bridge and likely the most accurate.
The 1831 Fifth Annual Report of the President and Directors to the Stockholders of the Baltimore and Ohio Railroad Company lists the bridge as 350 feet and 3 inches in length, 23 feet and 8 inches wide, and reported the cost at $26,118.31. The "Annual Report" also described the bridge as follows:
It is so constructed that its floor forms a roof impervious to water, and securely protects the timber beneath from the weather. The sides are to be weather boarded and painted. The masonry in the abutments and piers amounts to about 3,000 perches. The piers are 10 feet thick at the top, and they as well as the abutments, were raised at a rock foundation at a slope of one inch to one foot altitude. They rise 22 feet above low water. The bridge was undertaken last November, by Mr. Lewis Wernwag. Every possible exertion has been made by that skillful and enterprising bridge builder, assisted by two of his sons, to complete the work within the time stipulated by contract.
Below is even more detail about the bridge from the Frederick Town Herald article (mentioned above) on November 19, 1831:
......The railroad being open for travel to Parr's Ridge, a distance of forty miles from Baltimore, the directors of the company made an excursion to examine the line of the road and the operations now in progress on the inclined planes, by which cars will be enabled to pass "the Ridge."
In addition we here present our readers with a description of a splendid bridge, or viaduct, over the Monocacy, constructed by Lewis Wernwag, esz., whose reputation as a scientific bridge-builder no one will question. The bridges constructed by him in various parts of the country have long been celebrated for their beauty, strength, and scientific adaptation to the difficulties encountered-but we regard that which we are about to describe as his "chef d'couvre," which will long remain a monument of his genius.
The bridge, or viaduct, crosses the Monocacy, a short distance below that constructed for the Washington Road about three and a half miles from Frederick - on one of the most romantic sections of the river, and at that point from which the lateral road diverges toward Frederick. It is formed of three arches, resting on very solid abutments and piers of granite, laid compactly in mortar, rising 23 feet above water-mark. [The distance] between the piers and the abutments, 105 feet 10 1/2 inches- 105 feet 7 1/4 inches- and 105 feet 11 inches. Length of the arches 109 feet 10 3/4 inches- 109 feet 9 inches- 119 feet 1/2 inch. Length of the bridge on the top 350 feet 3 inches. Width 23 feet 8 inches. Water way under the chord 26 feet.
The objections to a viaduct with a roof arose from the intended use of locomotives, and induced Mr. Wernwag to combine a principle that would remove them. Accordingly, the floor of the bridge is decked like that of a ship, the seams being caulked with oakum and well pitched; thus rendering it completely impervious to water. The whole work is so constructed as to admit of repair without arresting the travel across it. The arches are entirely loose between the king-posts and braces, and they rest in cast-iron "shoes," which rest on keys, by which means the arches can be raised at pleasure. The king-posts and braces keep the arches in their proper position and prevent them from settling unequally. The whole of the timber has been "sawed through the heart" as the phrase is, and is kept apart (to prevent the dry-rot) without mortise or tenon, being held together with screw bolts, which are so placed that, as the timber seasons, they can be screwed up. The arches are of the lateral construction, that is, with an inclination towards the center, braced together with diagonal braces connected with the abutments. The joist and floor beams are screwed with a double set of bolts to the stretchers, the whole being so secured as to bid defiance to the winds with all kinds of lateral motion. The wood-work is secured by weather-boarding, and the top of the viaduct surmounted with a neat railing.
Unfortunately, the Monocacy Railroad Bridge burned down on March 17, 1854. The Baltimore Sun published an article about the demise of the bridge on March 18, 1854:
BURNING OF THE MONOCACY BRIDGE--We regret to learn by telegraphic despatches (sic) received in this city yesterday that the Monocacy Bridge of the Baltimore and Ohio Railroad was yesterday afternoon so far burnt as to prevent the passage of the trains.
The bridge is a tolerably high one, and, of considerable length, constituting it one of the most important on the road; yet we are informed such promptness and efficiency of effort will be, and even yesterday was already on foot, for effecting a means of regular passage over the river, that the suspension of transportation will be only the most temporary. The heavy trussels kept in readiness along the road will be immediately brought into requisition for this purpose. The bridge was a covered one, with a zinc protection, and the fire is understood to have been occassioned by the sparks of a locomotive lodging in the timbers and boards under the metallic roof.
A follow-up article in the Baltimore Sun on March 20th provided a detailed account of the burning of the bridge:
THE RAILROAD BRIDGE AT MONOCACY--We gave in our paper on Saturday the first published account of the burning of the bridge over the Monocacy river. This important structure was on the line of the Baltimore and Ohio railroad, 50 miles from Baltimore, at the junction of the branch railroad to Frederick city, which is 2 and a half miles distant. On Friday last, the accommodation passenger train from Wheeling passed over the bridge, on its way to Baltimore, at ten minutes before three o'clock. At ten minutes past three, the bridge was observed to be on fire near the eastern abutment. The alarm was instantly given, and a messenger dispatched to Frederick for aid. Some road hands were soon gathered, and a few residents of the country within a mile or two of the spot also speedily appeared on the ground. Mr. James Clarke, an energetic officer of the road department, who was in Frederick at the time, repaired to the scene to direct the operations in attempting to rescue the bridge. No effort, however, could avail. The wind was blowing so strongly from the north-east that the fire was driven across toward the western end so rapidly and the smoke became so dense that all effort was useless. So quick, indeed, was the action of the flames, that in less than ten minutes after discovering the smoke the greater portion of the wood work was in a blaze, and in less than thirty minutes the burning ruins of the whole structure had fallen with a tremendous crash into the waters of the Monocacy.
The fullest preparations were at hand on Saturday morning for re-building the bridge as to pass the trains over, and on last night the entire range of the heavy trestling which is being erected to sustain the sills with the iron track of the road, was put together and placed in its position in the river. By tomorrow morning, therefore, or at the latest, on tomorrow evening, the entire tonnage operations of the road may be fully resumed, by the running of trains over the new structure.
The new bridge was finished on March 22nd through the efforts of nearly 80 workers. The new bridge was 60 feet from the water level and 350 feet long.
By mid-August the B&O Railroad decided to replace the wooden Monocacy bridge with an iron Bollman truss structure. On September 28, 1854, the Baltimore Sun announced the near completion of the iron bridge, reported to them by the Frederick Examiner:
AFFAIRS IN FREDERICK COUNTY--Monocacy Viaduct--For a week past the passenger trains have been passing over one track of the new iron bridge of the Baltimore and Ohio Railroad over the Monocacy; and we learn that by Friday next the entire structure will be completed and ready for general use. The bridge is represented to be one of the largest and finest on the line.

¹ Michael Caplinger, Bridges Over Time, A Technological Context for the Baltimore and Ohio Railroad Main Stem at Harpers Ferry, West Virginia (West Virginia University. Institute for the History of Technology & Industrial Archaelogy: 1997), p. 17.

UPDATED: May 15, 2013 to include a detailed article from the Frederick Town Herald on November 19, 1831. Date for building the bridge changed from 1833 to 1831 and changed the length of the bridge from 345 feet to 350 feet..

UPDATED: January 9, 2014 to include detailsabout the bridge from the B&O "Annual Report."

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