Coming back from Nam November 1971: Went Oakland to Alexandria VA, without a break, but by sleeper Denver to Chicago.
Oakland to Denver: At that time was on the UP across Wyoming, then pulled backward Cheyenne to Denver. The train length essentially doubled east of Denver. Had a UP dome which I spent a good bit of time in across the Sierra. A Burlington dome was added at Denver.
Chicago to Alexandria on the James Whitcomb Riley or George Washington, forget which name was being used. Fast down the ICRR tracks to Kankekee, then very slow and rough on the PC tracks across Indiana, then a nice ride, much of it in a dome across West Virginia. The dome was taken off in Charlottesville.
I don't believe Amtrak ever acquired a UP dome car....most of those went to the old Auto Train Corporation, other than what UP kept. What you probably rode was one of those "Three quarter length" SP dome lounges, with a lower profile. I believe at the time, was the only domes the SP permitted on their Donner Pass line....
From Denver east, they added regular Vista Domes, as well as Slumbercoaches to the consist.....
The dome car on you rode into Charlottesville went on with other cars to Newport News. The train was 'split' at Charlottesville.....