The 600-ton Big Boy locomotive left the Pomona fairgrounds on its way to a Union Pacific rail yard in Colton, about 60 miles away, where it will be available for two weekends of public viewing before moving on to Cheyenne, Wyo., for restoration work. The goal is to eventually get Engine 4014 back on the rails, said Union Pacific spokesman Aaron Hunt.

The engine, which weighs 1.2 million pounds when its fuel car, or tender, is included, was one of 25 massive steam engines that began riding the transcontinental rails in 1941.

It pulled heavy freight trains over the Wasatch Mountains between Ogden, Utah and Green River, Wyo., and retired after a 17-year career.

In 1962, the behemoth was donated to the RailGiants Train Museum in Pomona.

Since November, the locomotive has been slowly moved across the grounds at the Pomona fairplex on 4,500 feet of temporary track.

On Sunday, Union Pacific pushed the locomotive onto the main tracks, where it will be towed by modern diesel freight locomotives 56 miles to Colton a last stop before heading to Wyoming. The repairs there could take several years, Union Pacific has said.

In exchange for getting No. 4014 back, Union Pacific plans to deliver diesel locomotive No. 3105, a caboose and a box car to the RailGiants museum, company officials said.