Jeff, I haven’t ridden them all of course as the state is quite large. Our State parks are pretty much open to mountain biking. French Creek has a great trail system with classic PA rocky gnar. Nockamixon “The Nox” has about 10 miles of purpose built Mtb trails. Mostly flow trails that you can just rip on. Berms, rollers, man made features etc. Good place to take the family or beginners so they can learn bike control and technique. Fun if your more advanced because you can see how fast you can go before you overshoot it into a tree. Blue Knob State Park is also excellent technical riding. Yeah, we get a lot of techy stuff here where the glaciers stopped back in the prehistoric days and dumped lots of rocks that they were carrying.
Within the city of Philadelphia we have over 50 miles of challenging and fun single track. Valley Green park in the Wissahickon “The Wiss” has about twenty miles of well marked multi use trails that range from flowy and fast to gnarly ass rocky descents, technical, rocky, and punchy stair step type climbs. Come out and visit sometime. Contact me and we’ll take you through the park. I’ll be willing to bet you can’t clean the whole Wiss. The Belmont plateau section of Philadelphia. Also has a great trail network and the Philly Pump Track. The trails in Belmont were built by hardcore Mtb people and you will get your log over technique some practice. Lastly, there’s Penny Pack park with at least 15 miles of tight twisty fun single track. It’s our location of choice for night riding. That’s all within the city limits of Philadelphia. So… there’s my PA riding haunts for what it’s worth.