Apheloria virginiensis – a “large” millipede
According to Wikipedia, this 2-inch-plus orange & black flat-backed millipede has been “reported to secrete cyanide compounds as a defense” – so don’t touch it! If you have touched it, make sure to wash your hands since “the toxic compounds it secretes are poisonous and can cause extreme irritation if rubbed in the eyes.” And, don’t bite one.
Otherwise, these insects are harmless, and beneficial. They love damp forest floors strewn with rotting wood and host to mosses and fungi. They eat these things, and are an important part of the forest life cycle.