On July 4, 1828, Charles Carroll of Carrollton, the last living signer of the Declaration of Independence and a director of the Baltimore and Ohio Railroad, laid the cornerstone for the Carrollton Viaduct and remarked, "I consider this among the most important acts of my life, second only to my signing the Declaration of Independence."
Completed in 1829, the railroad named the 300-foot stone for Charles Carroll of Carrollton. The bridge carried the Baltimore & Ohio Railroad over the Gwynns Falls, its first major stream crossing as it headed west from its Pratt Street terminus. Worried about competition from canals, Baltimore's business leaders cast their lot with a new untested technology, railroads. Horses initially pulled the loads, but the B&O successfully introduced steam-powered locomotives and became known as "the Railroad University of the United States"
By 1880, the railroad helped make Baltimore a major livestock and coal terminal and the second largest port for grain in the nation. Carrollton Viaduct has endured and is now the world's oldest active railroad bridge.