A majestic limestone formation at the southernmost end of the Guadalupe Mountains in Guadalupe Mountains National Park, Texas. El Capitan was once an enormous reef submerged in a Permian sea. Over the course of two hundred and fifty million years, the reef was buried only to be exposed later due to tectonic uplift and erosion of the surrounding sandstone. El Capitan is now a mountain of highly fossiliferous limestone containing skeletons of algae, sponges, bryozoans and other sea creatures.

Standing thousands of feet (8,085 feet above sea level) above the relatively flat lands of Texas, El Capitan can be seen from miles away. It was used as a landmark by early settlers.