Thank you for your question. The snake in the photo is a black ratsnake, scientific name Pantherophis obsoletus. Some herpetologists have separated the northern population of this species into a separate species, Pantherophis alleghaniensis. It is a non-venomous species.
The juveniles have a grey background with black saddles, but, as they get older, they get progressively darker, until they are almost completely black, except for a white chin and light colored stomach. However, the remnants of the pattern on the back can still be seen on some individuals.
The black ratsnake is found from Vermont west to Wisconsin and south to Kentucky, Tennessee and Georgia.
Average length for this species is between 4 and 5 feet, and maximum length is over 8 feet. These snakes are excellent climbers and powerful constrictors. They feed on rodents, birds, young squirrels, bird and chicken eggs.
Here's a link to the PA Herps website's species page for the black ratsnake:
If you are interested in learning more about the snake species in your area, here is an excellent field guide:
Gibbons, Whit. (2017). Snakes Of The Eastern United States. Athens: The University of Georgia Press.
I hope this answers your question, and thank you for contacting Ask an Expert.