Algodones Dunes at 45 miles long and 6 miles wide is the largest sand dune ecosystem in the United States and is located in the southwestern part of California near the Arizona and Mexican borders. To the east are the Chocolate Mountains. The dunes were apparently created by wind-blown sands from ancient Lake Cahuilla, an ephemeral lake created more than once during periods when the Colorado River flowed westward toward the Salton Sink. As late as 1450 the most recent Lake Cahuilla covered much of the Coachella, Imperial and Mexicali Valleys. State Route 78 runs east-west through the dunes, and the area north of that highway has been protected from off-road vehicle access and is where the great majority of the flora is. South of the highway is a mecca for off-roaders and consequently has been almost completely denuded of vegetation.

Rush milkweed
Asclepias subulata
Asclepiadaceae

Fanleaf crinklemat
Tiquilia plicata
Boraginaceae

Honeysweet
Tidestromia oblongifolia
Amaranthaceae
]Named for Ivar Theodor Tidestrøm, 1864-1956

Algodones Dunes sunflower
Helianthus niveus ssp. tephrodes
Asteraceae

Desert sand verbena
Abronia villosa var. villosa
Nyctaginaceae

Desert marigold
Baileya multiradiata var. multiradiata
Asteraceae
[Named for Jacob Whitman Bailey, 1811-1857

Emory indigo bush
Psorothamnus emoryi
Fabaceae
[Named for William Hemsley Emory, 1811-1887]

Coulter's globemallow
Sphaeralcea coulteri
Malvaceae
[Named for Dr. Thomas Coulter, 1783-1843]

Sand food
Pholisma sonorae
Lennoaceae

Giant Spanish needles
Palafoxia arida var. gigantea
Asteraceae
[Named for José Rebolledo de Palafox y Melzi, 1776-1847

Creosote bush
Larrea tridentata
Zygophyllaceae
[Named for Juan Antonio Hernández Perez de Larrea, 1731-1803

Palo verde
Cercidium floridum ssp. floridum
Fabaceae

Dune buckwheat, Colorado Desert buckwheat
Eriogonum deserticola
Polygonaceae

Lax flower
Baileya pauciradiata
Asteraceae
[Named for Jacob Whitman Bailey, 1811-1857

Wiggins's croton
Croton wigginsii
Euphorbiaceae
[Named for Ira Loren Wiggins, 1899-1987]