During the 1870-1880 period, he worked for Barlow, Sanderson Stage Lines and others (e.g. Wells Fargo, Majors and Waddell) in and around Kit Carson County, Colorado.
In letters to another relative Lewis "Lew" Barnum (1906-1990), a granduncle of Thomas, mentioned that Thomas died a few years after his younger brother Lewis (1830-1876). Lew went on to say that Thomas' widow stayed in Kit Carson and left everything to her church when she died. Thomas was in Colorado by 1870 (the Census listed his age as 40) and married Agnes Tunnlilty in Clayton, Missouri, also according to Lewis Barnum.