Some of these cases did appear in press accounts, when reporters depicted them as violent public spectacles, as they did with many lynchings of African-Americans in the South. For example, on July 5, 1851, a mob of 2,000 in Downieville, Calif., watched the extralegal hanging of a Mexican woman named Juana Loaiza, who had been accused of having murdered a white man named Frank Cannon.

Such episodes were not isolated to the turbulent gold rush period. More than a half-century later, on Nov. 3, 1910, a mob snatched a 20-year-old Mexican laborer, Antonio Rodríguez, from a jail in Rock Springs, Tex. The authorities had arrested him on charges that he had killed a rancher’s wife. Mob leaders bound him to a mesquite tree, doused him with kerosene and burned him alive. The El Paso Herald reported that thousands turned out to witness the event; we found no evidence that anyone was ever arrested.

While there were similarities between the lynchings of blacks and Mexicans, there were also clear differences. One was that local authorities and deputized citizens played particularly conspicuous roles in mob violence against Mexicans.

On Jan. 28, 1918, a band of Texas Rangers and ranchers arrived in the village of Porvenir in Presidio County, Tex. Mexican outlaws had recently attacked a nearby ranch, and the posse presumed that the locals were acting as spies and informants for Mexican raiders on the other side of the border. The group rounded up nearly two dozen men, searched their houses, and marched 15 of them to a rock bluff near the village and executed them. The Porvenir massacre, as it has become known, was the climactic event in what Mexican-Americans remember as the Hora de Sangre (Hour of Blood). It led, the following year, to an investigation by the Texas Legislature and reform of the Rangers.

Between 1915 and 1918, vigilantes, local law officers and Texas Rangers executed, without due process, unknown thousands of Mexicans for their alleged role in a revolutionary uprising known as the Plan de San Diego. White fears of Mexican revolutionary violence exploded in July and August 1915, after Mexican raiders committed a series of assaults on the economic infrastructure of the Lower Rio Grande Valley in resistance to white dominance. The raids unleashed a bloody wave of retaliatory action amid a climate of intense paranoia.