South of Salida, the 180-mile Rainbow Trail runs from Marshall Pass to the San Juan Valley sand dunes paralleling the eastern flank of the mighty Sangre de Cristo Range.  The trail offers an outstanding trip to riders with a wide variety of terrain and forest settings, as well as some excellent scenery and viewpoints along with numerous side trails to streams, lakes end mountain peaks. The Rainbow Trail, so called because it resembles a rainbow in shape, came into being with the settlement of the Wet Mountain Valley and the Upper Arkansas River.
--excerpts from gorp.away.com

The NW end of the Rainbow at Silver Creek.