From the trailhead, hike NW about 100 yards along the old road track and then veer off on a cairn marked trail that leads into sparse trees and willows. Continue on the trail as it leaves the last trees and begin ascending on tundra slopes. As you hike along, you may notice little markers in the tundra, left possibly for some kind of tundra/climate study. Please do not disturb these. The trail cuts through willows - almost all of which are low and pose little problem in getting through. At about 11,900 feet, the trail ascends to another bench–like area along the SE ridge and begins to fade out. Continue in a WNW direction, just following the ridge as it ascends more steeply beginning at about 12,200 ft. Almost all the hiking to the summit is on tundra with just a few rocky areas thrown in. In fairly short time, if you stay on the ridge, you will crest the 12,871 marker along the ridge. Drop down a little and cross the broad basin over to the summit. Along the way, you will see quite a few mining ruins and also as you approach the summit. Except for the final hike to the summit, it is almost all on tundra/grass. This entire excursion is in our thinking a class 1 hike – very easy. About the only excitement is the view NW from the summit where it drops precipitously down. You can also enjoy a nice view of London Mountain, across the way – perhaps your next destination for the day?
It's also possible and relatively easy to head over from Pennsylvania Mtn. to the WSW by way of an adjoining ridge and hike to Mt. Evans B and/or Dyer Mtn. The largest part of this hike would still be on tundra with some other typical rubble & scree thrown in.
For a return trip, just follow your ascent route back. Our time: We left our car at 9:00 AM, made the summit by 10:10, and were back at the car by 11:15, all the while, just taking our time and not hurrying at all.
Links to other information, routes & trip reports for this peak that may be helpful.