Youngstown Interchange Rail Viaduct
This imposing Pensylvania truss bridge seems to have carried a now-abandoned interchange between the Erie RR and the B&O RR. When I visited in 2008, the lower track was a Norfolk Southern line running on the north side of the Mahoning River which, from historic maps, seems to have been an old Erie RR line. There is a CSX line running on the south bank of the Mahoning River which seems to have been an old B&O RR line. The abandoned section of track that included this viaduct seems to have split off from the B&O line just west of Market Street, then crossed the Mahoning River a couple of times (also on abandoned bridges) before meeting the Erie RR near a (now-abandoned) steel mill just north of Division Street.
The Public Utility Commission of Ohio has an online RR map generator that includes abandoned lines, but it does not provide enough detail of interchanges to determine exactly what is what.