Juan Bautista de Anza made two expeditions through this terrain — one in 1774 to prove the route, another in 1775-1776 to establish the settlements the Spanish Crown wanted to plant along the California coast and at San Francisco Bay. Both times, the route through the Imperial Valley and up through the Colorado Desert required locating water in a landscape that offered very little of it above ground. At the San Gregorio campsite in the Borrego Valley, the expedition dug wells in a dry wash — an arroyo that carried water underground long after the surface had dried. The underground water comes from Coyote Creek's flow, which percolates into the sandy valley floor and can be reached by digging. For an expedition with 140 horses and a substantial herd of cattle, that underground water was essential. The Juan Bautista de Anza National Historic Trail now marks the route, and the historical landmark preserves this specific campsite.

Coyote Creek is 18 miles long, running from the city of Anza in Riverside County southward into the Borrego Valley. Despite its modest size, it holds a distinction that matters enormously in the desert context: it is the only reliably perennial stream in Anza-Borrego Desert State Park. It does not always flow at the surface — desert creeks can flow underground for long stretches — but it maintains enough consistent moisture to support the riparian corridor that makes the creek a biological oasis in the surrounding dryness. The creek divides into three vegetation zones: Upper Willows, Middle Willows, and Lower Willows, each characterized by willows, cottonwoods, and associated riparian plants that shelter a remarkable variety of birds and provide desert bighorn sheep access to water.

Long before de Anza dug his wells at the Borrego Sink, the Cahuilla people lived along Coyote Creek. The creek's reliable water and its associated riparian vegetation — the willows, cottonwoods, mesquite, and palms that the creek supports — provided resources that made permanent habitation possible in a desert that would otherwise be uninhabitable. The Cahuilla's knowledge of Coyote Creek's underground water, its seasonal flow patterns, and the locations where wells could be dug was likely part of the indigenous geographic knowledge that Spanish expeditions benefited from, whether through direct information exchange or simply by following the water sources that indigenous people had always used. The Borrego Sink as a campsite was not de Anza's discovery; it was already known.

During rainstorms, the Borrego Sink transforms. Water that falls across the valley collects in the flat depression, and the Sink can become a shallow lake — sometimes extending across a vast mud flat — before the desert heat and permeable soil return it to dryness. The bird life that Coyote Creek supports is seasonal and varied: Bell's vireo, black-crowned night heron, common yellowthroat, American kestrel, yellow-breasted chat, prairie falcon, red-shouldered hawk, and the black-shouldered kite all use the riparian corridor at different times of year. Desert bighorn sheep navigate between the creek's water sources and the higher terrain. The ocotillo and brittlebush visible from the historical marker near Palm Canyon Road give way to the richer vegetation of the creek corridor just minutes away — a concentration of life that the desert's logic makes comprehensible once you understand where the water is.