The B&O Railroad Museum is a museum and historic railway station exhibiting historic railroad equipment in Baltimore, Maryland. The Baltimore and Ohio Railroad (B&O) company originally opened the museum on July 4, 1953, with the name of the Baltimore & Ohio Transportation Museum. It has been called one of the most significant collections of railroad treasures in the world and has the largest collection of 19th-century locomotives in the U.S. The museum is located in the Baltimore and Ohio Railroad's old Mount Clare Station and adjacent roundhouse, and retains 40 acres of the B&O's sprawling Mount Clare Shops site, which is where, in 1829, the B&O began America's first railroad and is the oldest railroad manufacturing complex in the United States.