Located over the Gwynns Falls stream near Carroll Park in southwest Baltimore, the Carrollton Viaduct is the first stone masonry arch bridge built for railroad use in the United States for the Baltimore and Ohio Railroad and is currently one of the oldest railroad bridges still in use in the world.
The bridge was named in honor of Charles Carroll of Carrollton, the last living signer of the Declaration of Independence and a director of the Baltimore and Ohio Railroad. He laid the cornerstone for the Carrollton Viaduct on July 4, 1828 and construction was completed the following year. He remarked,
“I consider this among the most important acts of my life, second only to my signing the Declaration of Independence.”
Source: Baltimore Heritage website