To start your journey we recommend the History Colorado* website.
History Colorado is not a single building, but includes a series of "registered" historic sites and properties throughout Colorado that were restored using grants provided by History Colorado. Plus other offerings:
Museums & Exhibits
Events & Programs
Plan Your Event
Since you came here for Railroading history, here are some useful short cuts:
The Search Page
Searching for "locomotives"
Searching for the "2912", the PRF locomotive located in Pueblo, CO
Searching for "railroads" where the results include specific restored artifacts like the
and special publications like "Railroads in Colorado, 1858-1948" which includes a link to download the 200 page National Park Service document "Railroads in America, The Historic and Technological Evolution of Colorado's Railroads, 1858-1948".