The Wheatland Hop Riot occurred at this spot in 1913. From California Historical Landmarks:
The Wheatland Hop Riot was one of the most important and well-known events in California labor history. A bloody clash occurred at the Durst Ranch on August 3, 1913, climaxing growing tensions brought about by the difficult conditions farm laborers at the ranch endured. The riot resulted in four deaths and many injuries. It focused public opinion for the first time on the plight of California's agricultural laborers, and resulted in new state legislation to regulate labor camp conditions.