If you like to track vintage power then the Union Pacific's North Yard in Denver, Colorado is a good place to visit. Here we see UP 1344 , an ex Denver & Rio Grande Western GP40-2 (you can tell by the blanked off nose lights) built in 1974, as well as UP 573, an ex Southern Pacific GP38-2 built in 1980, and finally UP 1817, which was originally built in 1972 as a SD40-2 and later rebuilt as a SD40N.
