Caja del Rio (Spanish: "box of the river") is a dissected plateau, of volcanic origin, which covers approximately 84,000 acres of land in northern Santa Fe County, New Mexico, United States.

The landscape of the Caja del Rio Plateau is generally flat to rolling terrain, with numerous steep cones rising up to 800 feet above the plains.

Along the eastern edge is Canada Ancha, an ephemeral stream that flows northward into the Rio Grande near Buckman.

Another deep canyon (approximately 400 feet in depth) runs along the southern edge of the Caja, cut by the Santa Fe River.

The western edge of the mesa is a large escarpment known as La Bajada (Spanish: "the descent"), which is easily visible to highway traffic traveling north on Interstate 25 from Albuquerque to Santa Fe.

The volcanism can be explained by the field's location, which is very close to the intersection of the Rio Grande rift and the Jemez Lineament.

[4] The Rio Grande rift is a result of extensional, (or divergent) tectonic forces exerted upon the American Southwest.

The hawaiites have unusual trace element compositions, suggesting they originated in the remnants of the Farallon plate known to lie below western North America.

The final phase, from 1.5 to 1.1 million years ago, was restricted to a small area in lower White Rock Canyon east of the Rio Grande.

Soils in the Caja del Rio are derived from Tertiary volcanic basalt flows and cinder cone eruptions.

The most prevalent vegetative communities consist of a pinon (Pinus edulis) and juniper (Juniperus monosperma) overstory with a short grass understory.

Another large community consists of open grassland, with blue grama (Bouteloua gracilis), galleta (Pleuraphis jamesii), and various species of Stipa being the most common grasses.

Common woody shrubs include chamisa (Chrysothamnus nauseosus), Apache plume (Fallugia paradoxa), four-wing saltbush (Atriplex canescens), and big sagebrush (Artemisia tridentata).

Predatory mammals known to live in the Caja del Rio include black bear (Ursus americanus), mountain lion (Felis concolor), bobcat (Lynx rufus), coyote (Canis latrans), fox (Vulpes spp.

Non-predatory mammals known to be present include Rocky Mountain elk (Cervus elaphus), mule deer (Odocoileus hemionus), raccoon (Procyon lotor), porcupine (Erethizon dorsatum), black-tailed jackrabbit (Lepus californicus), desert cottontail, (Sylvilagus auduboni), white-throated woodrat (Neotoma albigula), Botta's pocket gopher (Thomomys bottae), Colorado chipmunk (Neotamias quadrivittatus), pinyon mouse (Peromyscus truei), and deer mouse (Peromyscus spp.).

Sensitive mammalian species known to be present at the Caja include Gunnison's prairie dog (Cynomys gunnisoni).

Other resident non-migratory birds include Merriam's turkey (Meleagris gallopavo), pinyon jay (Gymnorhinus cyanocephalus), hairy woodpecker (Picoides villosus), and scaled quail (Callipepla squamata).

Migratory birds found in or near the Caja include turkey vulture (Cathartes aura), killdeer (Charadrius vociferus), loggerhead shrike (Lanius ludovicianus), common nighthawk (Chordeiles minor), mourning dove (Zenaida macroura, broad-tailed hummingbird (Selasphorus platycercus), ladder-backed woodpecker (Picoides scalaris), downy woodpecker (Picoides pubescens), northern flicker (Colaptes auratus), gray flycatcher (Empidonax wrightii), Say's phoebe (Sayornis saya), ash-throated flycatcher (Myiarchus cinerascens), Cassin's kingbird (Tyrannus vociferans), plumbeous vireo (Vireo plumbeus), horned lark (Eremophila alpestris), violet-green swallow (Tachycineta thalassina), northern rough-winged swallow (Stelgidopteryx serripennis), blue-gray gnatcatcher (Polioptila caerulea), western bluebird (Sialia mexicana), mountain bluebird (Sialia currucoides), Townsend's solitaire (Myadestes townsendi), American robin (Turdus migratorius), American pipit (Anthus rubescens), black-throated gray warbler (Setophaga nigrescens), western tanager (Piranga ludoviciana), chipping sparrow (Spizella passerina), lark sparrow (Chondestes grammacus), western meadowlark (Sturnella neglecta), and brown-headed cowbird (Molothrus ater).

Sensitive bird species known to be present at the Caja include bald eagles, peregrine falcons, and gray vireos.

Prehistoric Puebloans built dozens of village sites across the Caja del Rio and Pajarito plateaus.

In contrast to its western neighbor, however, the canyon walls of the Caja are frequently made of basalt, rather than welded tuff.

From the beginning of colonization until the 19th century, subsistence users treated the plateau as common property, and used it for summer grazing and timber harvesting.

That acreage forms what is today the Caja del Rio Unit of the Santa Fe National Forest.

The Caja is now managed as a geographically distinct unit of the Espanola District of the Santa Fe National Forest.

That capacity is divided among twelve permittees who graze 492 cow-calf pairs and 28 bulls on ten pastures, in a yearlong season.

[11] The United States Forest Service has designated Caja del Rio a Wild Horse Territory,[12] and manages a herd of mustangs there.