Union Pacific's  legendary steam locomotive no. 844 will leave Cheyenne Thursday morning pulling a special 150th Anniversary Commemoration civil war troop train with nearly 300 civil war historians on board. U-P spokesman Mark Davis says the train's eventual destination is Marion, Ark. From there the historians will travel to the Shiloh Battlefield in Tennessee  for the 150th anniversary of that civil war battle. The train is expected to leave Cheyenne around 8am Thursday, according to Davis.