Completed in 1835, the Thomas Viaduct is the world’s oldest multiple-arch stone railroad bridge. Situated over the Patapsco River near Relay, Maryland, the structure was built by the Baltimore & Ohio, and has continuously served the railroad and its successors for one hundred eighty-five years. When the owner’s name was stated in words and not meaningless initials, a westbound Baltimore and Ohio auto rack train was on its way from Baltimore to Washington.
