It's not impossible for a mountain lion to be living in the Commonwealth. But it's unlikely. Pennsylvania has more roads and hunters that just about every other state in America. So, it would be difficult for a mountain lion to avoid detection. Sightings or tracks surely would be noticed.
In 2011, a mountain lion migrated from South Dakota to Connecticut, a journey of some 1,500 miles. It was discovered when it was killed by a vehicle while crossing a highway. DNA tests confirmed the big cat originated in South Dakota and that it also previously had been tracked in 2009 and 2010 through Wisconsin and Minnesota, where the animal's DNA had previously been collected through blood, hair and droppings.
The Game Commission periodically receives reports and photos of mountain lions. Our investigations have determined the overwhelming number of sightings of mountain lions in our state are actually bobcats. Photos submitted as mountain lions typical are feral housecats. Mountain lions have appeared in Pennsylvania in the past 75 years, but when they're captured, it's quickly determined they were formerly exotic pets or show animals. Pennsylvania's last known wild eastern mountain lion was killed in Berks County in 1874. And, except for Florida, the eastern mountain lion is believed to have extricated from the east coast by 1900. But as the South Dakota mountain lion proved in its at least unusual migration to Connecticut, anything is possible.