Pennsylvania #1361, one of their K-4 class Pacifics, was built in 1918 and then served through to 1958. At that point it was set aside for preservation (along with sister #3750, which hauled President Warren G Harding's campaign train and funerary train), named the Pennsylvania State Steam Locomotive and stuffed and mounted at Horseshoe Curve in Altoona. In 1985, the #1361 was removed from display and restored to operation by the Railroader's Memorial Museum in Altoona using state money. It entered excursion service in 1986, but by the accounts I've read from some people who worked on it then, it never operated correctly then and was constantly plagued with minor mechanical issues, as well as some crew members who were not the most knowledgeable.
In 1987, it had a minor derailment in York, PA that dislodged the grease cake from the axle bearing. It was rerailed, but nobody crawled underneath and noticed that the axle was no longer in contact with the grease cake. At the lower speeds around York, it was okay, as it never operated fast enough to get the axle hot. But on another excursion over main lines, it began to run hot, as the axle had no lubrication. When they stopped it, the axle grease was on fire, and a crew member grabbed a water hose from the tender and hit the red hot axle with cold water from the tender and cracked the axle. This ended it's year long excursion career and it was limped back to Altoona and put back on display.
In 1996, the #1361 was dismantled and moved to Steamtown to be restored in a joint effort between Steamtown, Railroader's Memorial Museum and University of Scranton, with the state again funding the effort. Over the course of 13 years, the state sank $1.7M into the engine, as almost every component of the locomotive needed repair or overhaul. There was also extensive deliberation over the boiler, which was worn very thing and already heavily patched. Steamtown wanted to replace but RRM wanted to patch the original boiler and keep it more original. In 2007, when funds ran out, and the locomotive was still disassembled, the smaller parts were all shipped back to RRM. In 2010, the plan changed to make the engine "Semi-operable" so that it could be steamed up and blow the whistle and move around RRM property at low speeds, but this was then abandoned because it would still have to pass FRA regulations and the boiler would not pass.
By 2015, all the parts had been removed from Steamtown, and the smaller parts were at RRM, while the bigger parts were being stored at the closed East Broad Top Railroad, with the plan being to just put the engine together to display again. Last year, a wealthy individual with a history of such projects, took charge of the #1361 project and has said that it will be restored to operation, it will be getting a new boiler to put to rest the concerns of the old one, it will be getting converted to roller bearing axles (using a blueprint that Timken drew up for PRR in the 1940s and still has on file!) both to avoid the problems of the first restoration and to make Class Is more conducive to allowing it to operate (some have a strict ban on any friction bearing equipment) and it will be touring the state. Hopefully that all comes true.