It rises to its greatest elevation of 1,900 feet (580 m) above sea level just southwest of Cunningham Falls State Park[3] and is transected by gaps at Braddock Heights (Fairview Pass), Point of Rocks on the Potomac River and Clarke's Gap west of Leesburg, as well as several other unnamed passes in Maryland and Virginia.

Its ridge character continues south of the Potomac in northern Loudoun County, losing elevation, until just north of Leesburg, where the range widens into a broad plateau of undulating hills separated by deep stream valleys.

South of the creek the Catoctin vanishes into the Piedmont countryside near the northern terminus of the Bull Run Mountains at Aldie.

The greenstone was originally formed about 570 million years ago as part of the rifting of the super-continent, Rodinia.

The greenstone was later uplifted during the Alleghenian Orogeny and thrust westward, being interspersed with the sedimentary rock deposited during the Paleozoic era.

[4] Catoctin Mountain is home to more than 280 species of animals, including amphibians, fish, arthropods, birds, reptiles, and mammals.

The nonnative brown trout population in the area is on the decline now that they are no longer being stocked yearly, but they were once plentiful in Big Hunting Creek.

The top ten most prevalent bird species found in the surveys they completed were the red eyed vireo, scarlet tanager, wood thrush, white-breasted nuthatch, American robin, eastern wood pewee, downy woodpecker, blue jay, eastern tufted titmouse, and red-bellied woodpecker.

Two of the snakes, the copperhead and the timber rattlesnake, are venomous, but elusive, living in the shattered rock and eating rodents or other small animals.

The resort is extremely well guarded by the United States Secret Service, and only approved guests of the president are allowed into the retreat.