Now, the trains are once again imperiled.

The Dunhams’ partner, John Couri, put up a substantial amount of money to open the attraction, but it never generated the traffic needed to turn a profit. Mr. Couri, of Ridgefield, Conn., now wants to recoup as much of his investment as he can, and is making the Dunhams sell off the trains at an online auction on Nov. 11.

The Dunhams hope that a wealthy patron will emerge, buy the railroads and keep them intact, perhaps in an exhibition back in Manhattan. Mr. Dunham said he and his wife would even continue to engineer the trains if that was what it would take.

“We’re hoping for an angel of mercy,” Mr. Dunham said. “We want it to have another life.”

Through the years the railroad has meant many things to many people. Joseph Ronga of Manhattan recalled how seeing the exhibit in late 2001 helped him escape the surreal and horrific memories of the morning of Sept. 11, 2001.

“My idea of entertainment is escape,” said Mr. Ronga, who worked for Sun Microsystems at 2 World Trade Center. “That’s what the train meant to me. I could watch it for hours. It was as much fun to see the delight in children’s faces as it was to watch it myself. It was very special.”