Every crawlspace is an adventure.  I don’t see that many in Pittsburgh, mostly basements and so I don’t know if that biases things, but often Pittsburgh crawlspaces are a mess.  In the older houses I spend all my time in, a crawlspace exists in because it was an addition they hit rock and gave up digging or both.  Below is the entrance to the crawlspace. 

Can you see the knob and tube?  This crawl space is original to the house. 

It is a stone foundation.  Above, the foundation stones were in disarray, water from a roof leak had eroded the mortar between the stones and rotted the end of two joists–someone shimmed a joist at the top of the photo.

Above is knob and tube wiring is frayed and degraded.