The Thomas Viaduct

Benjamin H. Latrobe II had a civil engineer legacy. His father, Benjamin Henry Boneval Latrobe, considered the “father of American architecture,” designed the Capital Building in Washington, D.C., the Baltimore Basilica, and the “Merchants’ Exchange,” one of nineteenth-century Baltimore’s most prominent buildings. The junior Latrobe would design and supervise the construction of the first multiple-arch stone railroad viaduct in the United States, which is still in use today, the Thomas Viaduct. 

A viaduct is a type of bridge that, unlike other bridges that traverse bodies of water, spans low-lying areas like valleys, which may or may not have rivers. The term comes from two Latin words, “via” or road, and “ducere,” meaning lead, and was not part of the vernacular until the early nineteenth century.

Spanning the Patapsco River and the valley between Relay and Elkridge, the Thomas Viaduct has eight arches, a style perfected by the Romans after they learned about arches from the Etruscans and built multiple-arch-stone aqueducts. The viaduct stands 60 feet above the Patapsco River and is 614 feet long, longer than the height of Transamerica Tower in Baltimore. The B&O Railroad’s first president, Philip E. Thomas, who researched the emerging rail system in England and, with other Baltimore citizens, secured a charter for the railroad company, is the viaduct’s namesake. 

Latrobe II joined the Baltimore and Ohio Railroad in 1830, the same year the company completed its first 13 miles of track from Baltimore to Ellicott’s Mills. He started with the railroad as a surveyor, during which he surveyed the route for a line from Baltimore to Washington. This rail line would be the one that needed the Thomas Viaduct. 

Work began on the viaduct on the Fourth of July 1833. The builder was a master mason from Ohio named John McCartney, who built a smaller viaduct for that first 13 miles of B&O track. Overseeing the project was Caspar Wever, chief of construction, who had worked on the National Road earlier. The major challenge the viaduct construction presented was building it on a curve. The granite used in its construction came from nearby quarries, and the viaduct included a wooden-floored pedestrian walkway. When it opened two years later, the line on top of the viaduct was the only rail line into Washington, D.C., until after the Civil War.

In 1859, as that war loomed, John Brown raided Harpers Ferry and attacked the B&O Railroad. Brown’s men seized trains, and rail traffic across the Potomac River halted. During the war, the B&O Railroad was the target of multiple attacks by the Confederates. In the spring of 1861, while Stonewall Jackson attacked and seized B&O property in the Shenandoah Valley and Harpers Ferry, Union forces under the command of General Benjamin Butler took over Relay, Maryland, to, among other things, protect the Thomas Viaduct from Confederate sabotage.

 General Butler, who later earned the nickname “spoons” for stealing silverware from the southern mansions he commandeered for his headquarters, placed cannons on hills overlooking the viaduct. Over 2,000 soldiers guarded the rail line and its viaduct. To prevent smugglers from using the line to bring supplies to the Confederates, passengers had their luggage and picnic baskets searched.

After the war, trains with passengers and cargo continued to travel across the Thomas Viaduct. The B&O Railroad dissolved in 1987, and CSX Transportation now owns the viaduct. The Maryland Rail Commuter has the Camden Line that runs over the viaduct several times a day, carrying loads much heavier than Benjamin H. Latrobe II envisioned when he designed this enduring structure.

Steve Bailey grew up in the Panama Canal Zone, was educated in Minnesota, and taught middle school for 32 years in Virginia. He can be contacted at vamarcopolo.com.