My understanding is that the Oregon Trunk consisted of the line from Wishram, WA to Bend, OR. What makes it murky is that the OT was a subsidiary of the SP&S, which was a joint subsidiary of the GN and the NP. The line from Bend to Bieber was the Great Northern's Klamath Division. I have a copy of Klamath Division Timetable #19 of 10/31/65, which shows the First Subdivision running from Bend to South Klamath (the GN yard in Klamath Falls), including 75 miles of trackage rights over the SP westward from Chemult. The Second Subdivision ran from South Klamath to the WP connection at Bieber, CA. I wonder what the reference to Stronghold was about; Stronghold is actually in California (about 31 miles from South Klamath) and is the location where the GN crosses the SP's Modoc Line at grade. There's no connection between the railroads there, so the place seems of little significance. I believe the trackage rights from Chemult to Klamath Falls are just that, with no joint ownership, but I'm not sure.