The B&O Railroad Museum is a museum exhibiting historic railroad equipment in Baltimore, Maryland, originally named the Baltimore & Ohio Transportation Museum when it opened on July 4, 1953. 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, part of the B&O's sprawling Mount Clare Shops site begun in 1829, the oldest railroad manufacturing complex in the United States.
The museum houses collections of 19th- and 20th-century artifacts related to America's railroads. The collection includes 250 pieces of railroad rolling stock, 15,000 artifacts, 5000 cubic feet (140 m³) of archival material, four significant 19th-century buildings, including the historic roundhouse, and a mile of track, considered the most historic mile of railroad track in the United States. Train rides are offered on the mile of track on Wednesday through Sunday from April through December and weekends in January. In 2002, the museum had 160,000 visitors annually.
The museum also features an outdoor G-scale layout, an indoor HO scale model, and a wooden model train that children will enjoy climbing on. From Thanksgiving through the New Year, local model railroad groups set up large layouts on the roundhouse floor and in select locations on the grounds of the museum. A museum store offers toys, books, DVDs and other railroad-related items.