Four O'Clock Factoid is a new daily feature on Track Twenty-Nine helping to get you through the workday with a bit of useless knowledge.
The Carrollton Viaduct is the world's oldest still-operating railroad bridge. Located in Baltimore, Maryland, the stone masonry structure carries CSX trains over Gwynns Falls. It is named for Charles Carroll of Carrollton, who considered laying its cornerstone the second-most important act of his life, after only signing the Declaration of Independence. It was built by the Baltimore and Ohio Railroad and was opened in November 1829.