The Original ‘California Zephyr’ was hauled by three railroads
CB&Q ‘Burlington’ from Chicago to Denver
https://railpictures.net/photo/354513/
D&RGW ‘Rio Grande’ from Denver over the mountains to Salt Lake City
https://railpictures.net/photo/560410/
And the Western Pacific took the zephyr the last leg to California.
https://railpictures.net/photo/646695/
https://railpictures.net/photo/470025/