More details. As I mentioned above I thought we had some of the Union Pacific portion and I was right. I have a book "Fifty Years of Union Pacific Steam Excursions" by Stagner andReisdorff. Here are the notes from the book.
06/06/1958 826/844 Cheyenne-Ogden. Ry & Loco Hist. Soc./CA-NV RR Hist. Soc.
Note 1: This excursion included the first railfan trip service for the 844(FEF 3 4-8-4). It was also the last UP steam fan trip operated during the regular steam era. The special, which originated at Oakland, operated via Western Pacific to Salt Lake City, then via D&RGW to Denver(With a side trip to Alamosa to ride the narrow gauge), and then Denver to Cheyenne via the Colorado & Southern(With a side trip to Loveland to ride the Great Western). This special then operated Cheyenne to Green River on June 6 with 4-8-4 No. 826, and Green River to Ogden on June 7th, with 844. The special then returned to California via the Western Pacific.
Special Note: 4-8-4 #844 was last used in regular freight service in November 1958, after which it was stored at North Platte. The engine was later moved to Council Bluffs for snow Melting service.
Greg's Note. UP 844 was never retired by the UP.
Greg Scholl