Railroads in NH were already starting the decline by the 1950s. But they weren’t dead yet and many of the locations that I feature on the NNES were still handling a fair amount of traffic. Below is a map of the Boston and Maine system showing the route of the layout highlighted.
The green line traces the route for the lowest level of the layout from Salem, MA to Portsmouth, NH. This constituted much of the B&M Eastern route between Boston and Portland, ME.
The blue line traces the route for the middle level of the layout from Haverhill, MA to Dover, NH along the old Western route between Boston and Portland, and then from Dover turns further north up to Wolfeboro and Ossipee.
The orange line traces the route from Conway NH through Crawford Notch and then over to the paper mill at Gilman VT.
I also show in purple the connections via the two helices between the lower and middle levels (Salem to Haverhill) and the middle and upper levels (Ossipee to Conway).