The Guadalupe Mountains are a mountain range located in West Texas and southeastern New Mexico. The range includes the highest summit in Texas, Guadalupe Peak, 8,751 feet, and the peak of West Texas, well known from even ancient times, El Capitan, both of which are currently located within Guadalupe Mountains National Park. The Guadalupe Mountains are bordered by the Pecos River valley and Llano Estacado to the east and north, Delaware Mountains to the south, and Sacramento Mountains to the west.

One of the clearest exposures of a prehistoric reef is preserved in the bedrock geology of this mountain range, which bedrock contains fossils of reef-dwelling organisms from the Permian period.

The reef traverses mostly underground in West Texas and Southeast New Mexico, but in three uplifted mountain ranges, the Guadalupe Mountains, Apache Mountains and Glass Mountains, the reef is exposed. These exposed reef areas are widely studied by those known as stratigraphers, paleontologists, and paleoecologists.