Here's the map of the route of the Zephyr train near Berkeley East to Denver and Chicago

https://www.amtrak.com/california-zephyr-train

It starts in the SF Bay area and goes through Reno, Nevada, Utah, Colorado, Nebraska, Iowa, Illinois to Chicago and the other way too.

In 2010 my wife and I and her friend rented the two biggest compartments on the train with 2 beds each and a sink and plug outlets and lights and a toilet and shower and a window to the outside. The only problem was I don't really sleep on planes or trains I realized. So, I missed my single nights sleep traveling across Nevada and woke up in Grand Junction, Colorado at dawn there. There is a 10 minute long tunnel (that no one can breathe in if they are outside the train or they would die by the way) which starts at about Winter Park, Colorado. So, if you were outside the train riding you would need a Scuba tank to survive these 10 minutes. Then after you cross the Continental divide through this tunnel you wind on down into Denver which is about 5000 feet in elevation. So, at one point you likely are between 8000 and 10,000 feet in elevation during your train ride in the Rockies. I've only ridden the train to Denver to visit my son who was studying in Fort Collins at a friends house for a College test. We drove back to California in his car then which was interesting doing that through Pueblo, Colorado, Taos, new Mexico, Santa Fe, new mexico, Winslow, Arizona, The Grand Canyon and I was so very glad to go wading in the Colorado River where it was still warm because Colorado and New Mexico and parts of Arizona around Flagstaff and the Grand Canyon were pretty cold then.

I'm used to much warmer weather living on the California coast. I haven't really lived in the snow since 1992 in Mt. Shasta except for skiing in Lake Tahoe and Mt. Shasta whenever I could over the years.