Located in the southeast corner of the Anza-Borrego State Park, the Fish Creek Wash Trail passes through a unique canyon known as Split Mountain. This canyon is unique because, unlike other canyons that lead into a mountain and ends, it passes entirely through the mountain – from one end to the other.

As the name implies, Split Mountain also splits the mountains in half and into two separate ranges, which are the Vallecito Mountains on the west and the Fish Creek Mountains on the east. Geologists claim that the canyon was formed when water was continually draining from the Carrizo Badlands in the west to the Salton Sink in the east. As the mountains rose over time, Fish Creek Wash continually gouged down into the new mountains creating the canyon.