How Did Passenger Trains from New York Reach Chicago?

[richhotrain]

@ATLANTIC_CENTRAL

B&O trains took a rather round about route from NYC to Chicago. Leaving NYC (and later from the Jersey City terminal) trains went to Philly, Baltimore and Washington DC, before heading west to Pittsburgh and on to Chicago.

I saw that when I was looking at the B&O track route map. What was the purpose of that round about route?

Rich