题目内容：
U.S. Marks 175 Locomotive YearsBuilt by the Mason machine Worlds in 1856, the 27,900-kilogram William Mason was an example of the archetypal 19th Century American locomotive, the oldest in operation in the United States. The locomotive was transferred last month from its open bay in B＆O's historic roundhouse to ready it for this summer's Fair of the Iron Horse, a celebration of 175 years of American railroading, in the city of Baltimore, Maryland. Tests will show whether the old gauges and boiler pressure points are up to federal standards to operate during the six-day festival.
“This is sort of the world's fair of railroading,” said Courtney Wilson, executive director of the B＆O Railroad Museum. The festival will run from June 28 to July 3 and display what organizers say is the most impressive collection of locomotives in the Western Hemisphere.
At the museum, an area will be set aside for model trains to keep toddlers interested. Children will learn about safety rules around train tracks. Adults will be able to track the development of railroad technology－from horse power to steam and diesel power to magnetic levitation, which can push trains at speeds upward of 390 kph.
“We have locomotives coming from all over the country, and we believe even the Rocket is coming from England--the very first locomotive in the world－to participate in this fair,” Wilson said.
The Rocket, the first successful steam locomotive in the world, won a competition in 1829 as the fastest locomotive—an event that helped spark worldwide railway interest.
“it was probably the fastest machine on Earth in its time,” Wilson said.
Rail companies in France, Canada, Germany and Spain have been invited to participate in this year's event.
“This will probably be the last time in this century that these many locomotives will be assembled in one spot, and it'll be a once-in-a lifetime experience,” Wilson said.
The B＆O Railroad was the host of a similar event in 1927 in nearby Hale Thorpe that attracted more than 1.25 million visitors over three weeks. The railroad held the event for its 100th anniversary.
Museum officials hope the event gives people a better appreciation of trains.
The museum's 22-sided roundhouse will be a focal point in the months leading up to the festival. Completed in 1884, the building rises 40. 5 meters into a huge cupola and covers nearly a half hectare of ground. The roundhouse has been in continuous use since its construction.
Inside is the most significant collection of railroad artifacts in the nation, including a replica built in 1926 of the Tom Thumb—the first American built locomotive (constructed in 1830)—and the St. Elizabeth—one of the last steam engines built in the United States(1950).
The museum, which sits on about 16 hectares in west Baltimore, holds locomotives, freight and passenger cars and other rolling stock－including cars from the nation's first trains, which were pulled by horses.
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