[PRCo] PRCo - "through?" lines

[mrb190]

Now that I see PAT, in recent years, has created routes which go all the way
from Bellevue to Highland Park, cutting through downtown Pittsburgh, it made me
recall reading that the railways once had such routes....

Wasn't there a route which went from the Butler Street 62nd street loop, through
town, and over to the South Side Carson Street loop (where route 50 once
terminated)?

Does anyone know of any others?

Also, is that what a "through" route is -- a route which travels through
downtown on to another destination?

Thanks,
Matt