The first two pictures Dave posted here are of RGW #2 (formerly 75, a number it wore on RGW/D&RGW & D&RG until re-numbered to 2 in 1892) a Class 56 engine the RGW converted to Std gauge in 1891. The picture with the un-finished water tank is the first train into Richfield, Utah in 1896.
The third picture is a bit harder. If taken before 1908 it is one the former #416 of the Class 75s engines the D&RG purchased in 1881 which was renumbered to 804 in 1908 to make for for the former RGW #1 (ex #03, UC #3) which was #554 from 1908 to 1924, when it became D&RGW 306, having been converted *back* to narrow gauge in 9/1918. I think it is the later.
The final picture is a bit harder, but the tag says it is 801, the future 411 which appears right to me. Guessing without the additional info I'd go with one of the Class 70 (1881) engines during its period as a standard gauge switcher anyway.
Hank