The park is situated near the southernmost reaches of the Cleveland National Forest, as well as the Cuyamaca and Laguna Mountains of the Peninsular Ranges.

The park's 26,000 acres (11,000 ha) of land features pine, fir, and oak forests, interspersed with meadows, creeks and streams that exist due to the relatively high elevation of the area when compared to its surroundings.

Native plants are, mostly, evolutionarily attuned to seasonal drought and fire ecology, and have since re-established in most areas; the large amount of ash, blackened wood and burnt plant matter greatly stimulates dormant seeds and undamaged saplings to sprout vigorously, as well as triggering a flush of growth from various bulbs and rhizomes lying hidden beneath the surface of the ground.

Cuyamaca's average elevation of nearly 5,000 feet (1,500 m) enables many conifers and broadleaf trees to exist; a rarity in xeric Southern California.

Migrants, transients and summer residents include the ash-throated flycatcher, Baltimore oriole, black-headed grosbeak, house wren, lesser goldfinch, several warblers, and the western wood pewee.

[8] 11 days after the park reopened, however, a different cougar nipped a girl playing with her family in the campground and fought with their dog.

[9] 1994 saw two separate incidents in which a cougar acted aggressively toward a party of three humans; officials located and shot both animals.

[8] Then in December 56-year-old Iris Kenna was killed during an early morning solo hike by a 130-pound (59 kg) male cougar, which was located and destroyed that night.

[11] Historical features in Cuyamaca Rancho State Park date from prehistoric humans through the Southern California Gold Rush.

In water-short Southern California, the native Americans called the area Ah-Ha Kwe-Ah Mac, meaning "the place where it rains".

Kumeyaay peoples' traditional lands range from San Diego east through the Cuyamaca and the Laguna Mountains through present-day Anza-Borrego Desert State Park to beyond the Salton Sea in the east, and south beyond present day Ensenada, Baja California, on the Baja California peninsula in Mexico.

With the discovery of gold in Julian in 1869, the Spanish, Mexican, and American governments and settlers changed the Kumeyaay's way of life forever.

Disease spread through the Kumeyaay, traditional ways of life were destroyed, and promises broken as the Indians were expelled in 1875 from ancestral lands and taxed without representation.

Sources of funds include profits from the operation of a gift shop and bookstore, sale of firewood, membership dues, and various fundraising events.