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
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.