If the letter displayed on the Soapy Smith's Soapbox blog is credible and not a fabrication of Smith or a descendant, Smith worked as a "train baggag" (sic) manager for the Denver and Rio Grande Railroad out of Pueblo for 14 months, ending in 1882. But hold on, it doesn't appear to be all it claims to be, as the blog lists several alternatives for the letter's origins.
For those unfamiliar, Soapy Smith was the con man's con man. From Denver to Creede, he ran games, swindled money and even charged money to view a "mummy" found in the mountains (the mummy was later found to be concrete). His end came not in Colorado, but Skagway, Alaska. Nonetheless, he was one of the most colorful characters to ride the railroads of Colorado.