The Wall Street Mill is the only gold ore-crushing mill in the Joshua Tree region that has retained its structural and mechanical integrity. Bill Keys built it using a two-stamp crusher manufactured by Baker Iron Works and a Western Gas Engine Company gasoline engine to power it, moving the equipment to this site from Pinon Wells. The mill also included a Myer concentrating table used to separate the gold from processed rock. A two-stamp mill is a relatively small operation — it could process a limited tonnage of ore per day — but for a single operator working claims in the desert, it was a practical scale. Keys operated the mill to process ore from various claims in the area, including his Desert Queen Mine.

The conflict that ended at the Wall Street Mill on May 11, 1943, began with something that sounds minor: a dispute over a road. Worth Bagley claimed rights to a road that ran through Keys's property; Keys disputed Bagley's access. In the Mojave Desert of the early twentieth century, where road access was the difference between a working mine and an isolated one, road rights were not minor matters. They were economic life or death. The dispute between Keys and Bagley escalated over years before the confrontation at the mill. Keys claimed self-defense. A jury convicted him of manslaughter and sentenced him to ten years at San Quentin. He served five years before parole.

Erle Stanley Gardner had made Perry Mason — the fictional defense attorney who never lost a case — into one of the most popular characters in American publishing. When Gardner became interested in Keys's situation, he brought to it the same investigative instincts that animated his fiction, and the same conviction that the justice system could be made to work correctly if the right pressure was applied in the right places. Gardner organized the campaign for Keys's pardon, and in 1956, Governor Goodwin Knight granted it. Keys was officially cleared of the 1943 killing. He returned to his ranch and his desert life and continued there until his death in 1969. That a literary figure of Gardner's stature would intervene in the fate of a desert rancher says something about both men.

The Wall Street Mill is now accessible by a short hike from the park road. The original equipment remains in place — the crusher, the engine, the concentrating table — preserved in the dry air that has kept metal machinery functional long past its working life. The site is part of Joshua Tree National Park's historic landscape, preserved both for its mechanical integrity and for the larger story it represents: the era of small-scale gold mining in the Mojave, the disputes that arose between isolated people over scarce resources, and the particular life of Bill Keys, whose presence saturates more of Joshua Tree's early human history than any other single individual. The stone marker Keys placed at the shooting site is, by some accounts, still visible in the desert.