Purisima Creek rises 1.3 miles north of Sierra Morena, a peak in the Santa Cruz Mountains, and flows westward through steep redwood canyons before opening onto the coastal plain. It reaches the Pacific Ocean 2.3 miles south-southeast of Miramontes Point, where it sometimes pools behind a sand berm before seeping through to salt water. The creek's watershed has been largely incorporated into the Purisima Creek Redwoods Open Space Preserve, which protects the dense forests and riparian habitat along its upper reaches. Four tributaries feed the main stem: Walker Gulch, Whittemore Gulch, Grabtown Gulch, and Soda Gulch, names that speak to the logging and mining camps that once dotted these canyons.

The Spanish Portola expedition of 1769 was the first European land exploration of Alta California, and its route through the San Mateo coast left marks that persist as place names and historical landmarks. The abandoned Torose village Crespi described near Purisima Creek represents one of many encounters between the expedition and indigenous communities already in upheaval. The Torose had moved into the mountains, their guides explained, a detail Crespi recorded without elaboration. What pressures had displaced them remains unclear, but the pattern of disruption would accelerate dramatically once the mission system took hold. The creek's campsite is now recognized as part of the broader network of California Historical Landmarks that trace the expedition's path.

In 1951, a skull fragment was unearthed one mile inland from the mouth of Purisima Creek. It belonged to a tule elk, a subspecies once widespread across California but hunted nearly to extinction by the 1870s. The California Academy of Sciences cataloged the find, a small piece of bone that told a large story. Elk were thought to be completely extirpated from the state by 1873, when the California Legislature finally banned hunting them. Every tule elk alive today descends from a small remnant herd discovered in southern San Joaquin County. The skull fragment at Purisima Creek is a reminder that this landscape once supported a very different community of animals, and that the quiet creek flowing through redwoods and grasslands carries ecological memory in its sediment as surely as it carries water.