On a typical Saturday, the B&O; Railroad Museum on West Pratt Street might attract 500 people. Today, museum staff members expect 5,000 or more.
The reason: Thomas the Tank Engine.
"Thomas is a superstar for 5-year-olds," said Shawn Herne, the exhibit's curator. "He's introducing railroading to a whole new generation of kids."
Hundreds of 3-, 4- and 5-year-olds will show up at the Baltimore train museum today for a chance to ride a 55-ton working replica of the sky-blue steam engine with the silly grin.
Some might stop to climb on the museum's collection of 19th-century railroad engines or lie on their backs to admire the 116-year old roundhouse cathedral, but not until they've seen the polite railroad engine first.
A family from Russia reportedly planned their trip to the United States around the Thomas exhibit at the B&O;, forgoing Paris and Disney World in favor of the fictional train.
Others follow the engine around the country. The exhibit will travel via flatbed truck to nine U.S. cities this year.
By tomorrow, the final day of Thomas' nine-day run, some 30,000 people are expected to visit the museum - most before nap time.
The exhibit, which is expected to gross more than $300,000, is the B&O;'s most popular event of the year.
"Thomas is everything," said Constance Julius of Waldorf as she snapped photographs of her 4-year-old, Hamilton, in front of the train shortly before it departed for its 1 1/2 -mile chug down the track.
Hamilton left his collection of Thomas the Tank Engine sheets, underwear, videos, rugs, books and alarm clocks and yes, trains, at home for the day, but his love for the plucky engine was apparent in his adoring gaze.
Thomas might not have Harry Potter's current sales figures, but he's been around longer. Compared to the terrific tank engine, J. K. Rowling's fictional boy wizard is still wet behind the ears.
Thomas the Tank Engine was created in 1943 by the Rev. Wilbert Vere Awdry, who made up stories about a little train to keep his young son entertained during a bout of measles.
More than 100 million Thomas the Tank Engine books have been sold worldwide since the book's debut in 1945.
The Thomas television series has been a hit in 20 countries. Thomas forks, lunchboxes and other products have turned the train into a powerhouse that grosses about $2.5 million a year.
And Thomas' first feature-film, "Thomas and the Magic Railroad," which stars Alec Baldwin and Peter Fonda, will hit movie theaters July 26.
Bill Hakkarinen, Franklin Square Hospital Center doctor by day and volunteer conductor for the week, attempted to explain Thomas' soaring popularity be-tween trips on the engine.
"There's a certain respect in [the books and videos]," he said. "They teach good values. They're also accurate from a railroading perspective."
The Baltimore exhibit - which includes an activity tent and a Ferris wheel - was meant to introduce a younger generation to the site of the first railroad chartered and built in the United States.
Many children swarming the B&O; grounds yesterday afternoon said they thought the Thomas replica was the actual train from the books and television series.
Museum staff members did not dissuade them.
"A 3-year-old came up to me, and he was very angry," said Hakkarinen. "He wanted to know why the caboose was right behind Thomas, not at the end of the train. I told him, 'Thomas wanted it there.'"
Summing up what the tank engine has to teach children, a Falls Church, Va., mother of 3-year-old twins said: "Be nice. Be humble."