The Natural Arches Trailhead is just before Elephant Rock. There's no sign on the road so just keep an eye out for an unpaved area on your left if traveling east to west through the park from I-15. The Natural Arches Trail heads north through brushy desert to a deep, red-sandy wash that you follow for as long as you want. Interestingly, as a sign at the trailhead notes, there actually isn't a definite end to the Natural Arches Trail, but most only hike for about 2.5 miles. Within those 2.5 miles you see almost all of the natural arches on a relatively well-defined trail. Like most of the longer trails in this area, it is recommended to only do this trail in its entirety in the cooler months; there is almost no shade and it can be very hot.