To answer the above question - YES the depot was added in 1971 to the original 32,800+ acre site which was placed in 1966 on the National Register.
It is also on the state of Colorado's register. Quote below:
SILVER PLUME DEPOT
Off I-70, south side of Silver Plume
National Register 5/6/1971, 5CC.4
The 1884 Silver Plume Depot served as the western terminus of the Colorado Central Railroad route from Denver to the Clear Creek mining region. Located at the upper end of the famous Georgetown Loop, the depot first served miners and their families, and then the increasing number of tourists attracted by the engineering and scenic qualities of the loop passage. The loop and the depot were abandoned in 1939, but both once again operate as part of a historical interpretive complex. Listed under Railroads in Colorado, 1858-1948 Multiple Property Submission.
On the link below, scroll down to find the depot listing.
JB