The NP Wallace branch that Bruce referred to included this spectacular trestle, uphill from Mullan ID:
[
i]An overhead view is really needed to properly appreciate the famous S bridge on the Wallace branch.[/i]
Photo from the Ron V. Nixon Collection here: [morphotoarchive.org]
A passenger train was involved in wreck on that same bridge in 1904. Photo here:
[
morphotoarchive.org]