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, 5,000 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.
The museum also features an outdoor G-scale layout, an indoor HO scale model, and a wooden model train for children to climb 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.
The museum and station were designated as a U.S. National Historic Landmark in 1961. In 2008, the Museum won three awards in Nickelodeon's Parents' Picks Awards in the categories of: Best Museum for Little Kids, Best Indoor Playspace for Little Kids, and Best Indoor Playspace for Big Kids. Television and film actor Michael Gross is the museum's "celebrity spokesman".
The museum also hosts an annual Day out with Thomas event every year. Complete with the train's excursion including a non-powered Thomas the Tank Engine replica built by the Strasburg Rail Road.