Take one of two well marked routes off US HWY 95 between Marsing ID and Jordan Valley OR. Either road is a 25 mile well maintained gravel road.
I had taken a similar shot during the day on a prevoius trip but figured a longer exposure after sunset would capture the best light.
Leslie Gulch is the closest place near Boise ID (where I live) to get my Southwest US fix. The rock isn't quite as red, but the formations and multiple gulches are very impressive and outstoundingly out-of-place.