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Thomas Viaduct Railroad Bridge Recognized as National Historic Civil Engineering Landmark

Mon April 15, 2024 - Northeast Edition #9
American Society of Civil Engineers

Opened in 1835, the Thomas Viaduct was the first multiple-arch, stone railroad viaduct in the United States.
Photo courtesy of The American Society of Civil Engineers
Opened in 1835, the Thomas Viaduct was the first multiple-arch, stone railroad viaduct in the United States.

The American Society of Civil Engineers (ASCE) dedicated a marker recognizing the Thomas Viaduct in Elkridge, Md., as a National Historic Civil Engineering Landmark.

The Thomas Viaduct is the first multiple-arch stone railroad viaduct built on a curving span in the United States. Construction on the Thomas Viaduct started in 1833 and opened in 1835. The 614-ft.-long, 58-ft.-tall span remains a crucial link in Maryland's rail infrastructure today, carrying freight and passenger traffic between Baltimore and Washington, D.C.

The dedication ceremony at Patapsco Valley State Park was led by ASCE's Maryland Section, The Maryland Department of Transportation (MDOT) Transit Administration, CSX Railroad and the B&O Railroad Museum.

ASCE represents more than 160,000 members of the civil engineering profession worldwide. It is the oldest national engineering society in the United States. ASCE recognizes historically significant civil engineering projects, structures, and sites worldwide. More than 270 projects have earned the prestigious title for creativity and innovation; almost all are executed under challenging conditions.

"As civil engineers build the infrastructure of the future, they take inspiration from the projects which helped shape communities today," said Marsia Geldert-Murphey, ASCE president. "The Thomas Viaduct played a huge role in developing rail service on the east coast nearly 200 years ago and remains a vital link every day for freight service, which delivers so many of the items we need to live our lives, along with providing efficient commuter service for thousands of people every day. The work of a civil engineer can impact a community for centuries, which is why it is so important to design projects for the future."

The Thomas Viaduct became necessary as the Baltimore and Ohio (B&O) railroad planned the first rail line into the nation's capital. Civil engineer Benjamin Henry Latrobe Jr. (1806-1878), who served as the railroad's engineer, designed the project. Latrobe faced several challenges in designing the Thomas Viaduct because crossing the Patapsco River required a curved path for the railroad. To achieve this, Latrobe designed the crossing using eight arches and piers in a trapezoid shape.

When it opened, the 63,000-ton granite viaduct was immediately recognized by engineers as an engineering success. It has survived significant floods that damaged other nearby viaducts. During the Civil War, the Thomas Viaduct was on the only rail line in and out of Washington, D.C., and Union troops heavily guarded it to ensure its safety.

The Thomas Viaduct became a National Historic Landmark in 1964, and ASCE first recognized the project as a National Historic Civil Engineering Landmark in 2010. The April 13th event featured the unveiling of a marker to recognize the Thomas Viaduct as a National Historic Civil Engineering Landmark.

For more information about ASCE's Historic Civil Engineering Landmark Program, visit

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