I can't believe I haven't reviewed the Great Allegheny Passage Rail Trail until now. It is such a…read morejewel and where I spend a lot of my free time riding my bicycle, especially during this crazy time we're in at the moment with COVID-19. (Note that it is not just for bicycles; walkers and runners also utilize the trail, just not motorized vehicles, so you don't have to compete with cars.)
I won't go into all the details of the trail; that is interesting in itself regarding its history, how long it's taken to get the land for the different sections, its steepness grade or lack thereof, all the different towns it goes through, etc. For all of that, I'll give you the very useful link:https://gaptrail.org/
What I will do is give you some highlights and what makes it a jewel to me.
It is 150 miles of mostly packed crushed limestone (with a bit of it paved between Pittsburgh and McKeesport) from the Pittsburgh Point Fountain (there's a marker on the ground near it) to Cumberland, MD. Most of it is on what used to be railroad beds and a bit of it is on streets (near downtown Pittsburgh and some in McKeesport). Because of the railroad bed usage, the path follows that grade (meaning gradual steepness with the sharpest elevation gain/loss being between the Eastern Continental Divide and Cumberland).
What all the preceding paragraph means is that it is a quite doable trail and comfortable to ride. The packed gravel means it is pretty close to riding on a road surface because it is so packed. The only time that is not true is usually after a downpour when there might be parts of it that retain water. The grade following the grade of the railroads means the gradual incline (if you're going from Pittsburgh to Cumberland) is pretty gradual and a steady 10mph is doable. From the Continental Divide to Cumberland is downhill and is quite easy; coming back is a bit more strenuous -- see the afore-mentioned link to see mileage and grade of that section.
I remember when I first heard about the trail; I had no concept of a rail trail to begin with so did not know what to expect in the least. If you're in the same boat, I will say that the trail is open from sun-up to sun-down, there are no street lights lighting the path on purpose though where it travels in spots may have lights for other purposes. It is mostly wide enough for say three bikes across, but don't do that! There is trail etiquette; learn it for everyone's safety and enjoyment -- stay to the right, single file and if you are riding 2 across for any reason, then pay close attention to passers; you'll need to be sure to listen to "on your left' or a bell or some audible signal that someone needs to pass you. On the converse side, if you're passing, pass on the left and issue an audible signal, etc. Just share the trail!
Also, some parts of the trail are shaded by trees lining the trail; other parts are in the sun for extended periods so wear sunscreen.
There are amenities all along the trail. That was important for me as a first-timer to know because I couldn't grasp at first if it was secluded, wilderness, or what. The GAP trail has so many towns, ballfields, restaurants, ice cream stands, portable restrooms every so many miles and parking trailheads plus a number of other cyclists on the trail that you won't feel that isolated and except for a couple spots (downtown Pittsburgh or Ohiopyle for example) you won't feel the trail is too crowded, either. Take water, snacks, an extra tube and you'll find you'll have what you need.
Do you need certain size tires (mountain bike/hybrid/road bike)? Some people debate that. I have a hybrid bike and am happy enough.
Favorite parts of the trail for me? I love the section between Myersdale, PA and Frostburg, MD. In that section is the Mason-Dixon line and the Eastern Continental Divide. I also love riding between Homestead and downtown Pittsburgh. Along that route is the Hays Eagle nest. And being downtown Pittsburgh on my bike is so much easier than navigating and parking a car.
And when you want to go further on your adventure than Cumberland, MD? It hooks up directly with the C & O Tow Path for another 184.5 miles to get you all the way to Washington, D.C. for a total of 334.5 miles. Many of us have taken several days in one stretch to ride the entire length between Pittsburgh and D.C. and it is quite the trip, and well worthwhile, as are many of the many sections of the GAP trail. It has such unique personalities with wildlife (there are deer, owls, groundhogs, rabbits just to name a few) and so many wildflowers along the way. You're following rivers along the route, as well, plus get to take advantage of PA's lovely state park, Ohiopyle. There are several campsites, hotels, and bed and breakfasts along the way, too.
I could go on and on but I recommend talking to others who have ridden the trail, look up Facebook webpages related to the GAP, get a trail book and google for more info.