Milpitas Wash is near the southern end of the Mule Mountains and the Opal Hill Mine. The landscape is primarily desert mountain foothills as well as wash and floodplain habitats. Visitors can see petrified palm roots that were once part of an ancient, lush landscape.
The Milpitas Wash provides critical habitat for Desert tortoise, mountain lion, long-eared owl, leaf nose bat, Merriam and Desert kangaroo rat, long tail and little pocket mice, Bullock’s and hooded orioles, towhees, white-crowned sparrow, Brewer’s sparrow, warbler, black-headed grosbeak, diamondback rattler, and the endangered Gila woodpecker. The Milpitas Wash region supports the largest Sonoran Desert woodland in North America. Most of the trees are legumes: mesquites, acacias, palo verdes, and ironwoods; and there are also desert willows. The abundance of old-growth trees, with most standing over 15 feet high, gives the area a lush character rarely found in the desert.
Threats to the area include unauthorized OHV use and mining.
Native Americans used creosote bush as a sunscreen and potent antioxidant for the treatment of blood poisoning and hepatic diseases.
Rock hounding: the Milpitas Wash Road passes by nearby Hauser Geode Beds, a popular winter haven for rock collecting. Fire agates and geodes are among the treasures often found.