The original classification scheme employed by the Denver & Rio Grande was based on locomotive weight. This scheme was replaced in 1924 by a new system based on tractive effort. These two schemes are reproduced below. Other classification systems such as those employed by the Rio Grande Western, e.g., cylinder size, and the Denver & Salt Lake are not shown.

Note that the 1924 date is "somewhat" arbitrary. Although the majority of Rio Grande locomotives were re-numbered and re-classified in 1924, some may have carried their old numbers and classifications beyond the end of 1924. Also, the 1956 date represents the end of steam on the Rio Grande. It is recognized that surviving Rio Grande steam locomotives still carry the road number and classification originally assigned in 1924.

* Class 77 locomotives were standard gauge engines from the Rio Grande Western that were originally narrow gauge. They were converted back to narrow gauge by the Denver & Rio Grande Western.

** Class L-96 is the classification that was assigned to the 3400-3415 series (originally 1060-1075) of 2-8-8-2's. These locomotives have also been referred to as class L-95. Technically, L-95 is correct since the tractive effort of these locomotives was 95,000 pounds. L-96 was used in this table in order to remain consistent with the Colorado Railroad Museum's "Locomotives of the Rio Grande."

*** This line appeared in "Locomotives of the Rio Grande."