999 is a 4-4-0 “American” type steam locomotive built for the New York Central and Hudson River Railroad in 1893, which was intended to haul the road's Empire State Express train service.

[1] In 1892, New York Central's General Passenger Agent, George Henry Daniels, proposed a new, fast locomotive be designed to publicize the Empire State Express at the upcoming World's Columbian Exposition in Chicago in 1893.

[4] After the 1893 Chicago World's Fair, the engine continued to pull the Empire State Express between Buffalo and Syracuse until 1899.

In the 1920s, it was given a new boiler and tender, operating local and branch line trains until 1924, when it was restored for exhibition at the Baltimore and Ohio Railroad's "Fair of the Iron Horse" the following year.

[6] Once the unit had arrived at the Museum of Science and Industry, the engine was displayed outside, where it began to decay after being exposed to the elements.