The Colorado & Southern was a subsidiary of the Chicgo Burlington & Quincy. Its line from Denver to Pueblo was largely abandoned in the 1930s or 1940s when the C&S obtained trackage rights over the DRGW/ATSF Joint Line.
A short segment of the C&S between South Denver and Connors lasted much longer but it too is now abandoned. The bridge at the location in the photo was removed in the early 2000s as part of an upgrade/widening of I-25 in the area.