I'm trying to find out when the BN abandoned the ex-NP trackage on this line. I think service was kept as far south as Pullman, WA/Moscow, ID. Any help would be appreciated.
I lived in Moscow in 1995/1996 and the line was abandoned east of Moscow by that point, but the track hardware was (mostly) intact all the way down to the CSP connection east of Lewiston. I believe it wasn't ripped up until sometime in the early-to-mid 2000s.
Today, most of the trackage within Moscow is in the process of being removed, with just a very short section east of the state line to serve a feedmill (which was adjacent to the UP line, but it is the NP line that survives between Pullman and Moscow). Several segments of the NP line have been converted to bike trails, along with the UP line from Pullman to Moscow. The line is operated by the Washington & Idaho Railway, and formerly by the Palouse River & Coulee City which had taken over in (about) 1996.