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Maryland's National Register Properties

Photo credit: Mark R. Edwards, 01/1978
Thomas Viaduct, Baltimore and Ohio Railroad
Inventory No.: BA-143, HO-80
Other Name(s): Latrobe's Folly
Date Listed: 10/15/1966
Location: B&O Railroad over Patapsco River, Halethorpe, Baltimore County, Howard County
Category: Structure
Period/Date of Construction: 1835
Architect/Builder: Designer: Benjamin H. Latrobe
NHL Date: 1/28/1964
Description: Constructed of local granite in 1835, the Thomas Viaduct has proven to be a lasting tribute to its designer, Benjamin H. Latrobe. The viaduct is 612' in length, formed of eight semicircular-arched spans varying in length from 58'-5" to 58'-10 1/2". Because of the route alignment at the time of its construction, the structure was built on a four degree curve and stands 59' above the Patapsco River. The floor is 26' wide, broad enough to hold a double track. In addition to the track, a wooden-floored walkway, 4' in width and supported by cast iron brackets, is located on the deck of the viaduct. To aid pedestrians, ornamental cast iron railings were erected upon the outermost edge of the walkway. The granite is ashlar, roughly squared and dressed, laid in cement mortar, with openings at the crown of each arch. Pilasters, made of the same material, run from the top of each pier to the base. Crude in execution, they visually support the massive form of the viaduct while enhancing the harmonious proportion and inherent grace of the Roman arches. Constructed in 1835, the structure contains 24,476 cubic yards of stone and cost $142,236.51 to build. To counteract deterioration, the viaduct underwent repairs in 1938, performed by the Baltimore and Ohio Maintenance of Way Department. The work consisted mainly of improvements for drainage and the application of a grout mixture to the stone spandrel filling. At an unknown date, railing blocks were removed from the north side of the deck and a bracketed walkway added, giving more lateral clearance. Thomas Viaduct is in excellent condition and has been in continuous service since its construction in 1835. Significance: Still in use today, the Thomas Viaduct, located on the Baltimore and Ohio Railroad line at the point where it crosses the Patapsco River, is the world's oldest multiple stone arched railroad bridge as well as America's earliest notable example of railroad bridge construction. Designed in 1835 by Benjamin H. Latrobe, a civil engineer and son of the architect of the same name, the bridge was the largest in the country, dwarfing all contemporary masonry works and marking the real beginning of the major railway structure in America. Still impressive today, the structure has required no major repairs or changes in its many years of service.


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