From 1910 through approximately 1920, the Texas Rangers conduct a decade-long campaign of extrajudicial killing, torture, and collective punishment against ethnic Mexican communities along the Texas-Mexico border, a period known as "La Matanza" (The Massacre) or "La Hora de Sangre" (The Hour of Blood). Historians estimate between 300 and 5,000 ethnic Mexicans—including both Mexican nationals and American citizens—are killed by Rangers, local law enforcement, vigilantes, and U.S. Army soldiers during this period.
The violence follows the collective punishment logic established in the post-Reconstruction South but is now applied to ethnic Mexican communities: individual acts of banditry, revolutionary activity related to the Mexican Revolution, or the 1915 Plan de San Diego raids by Mexican insurgents trigger mass reprisals against entire Latino communities regardless of individual involvement. Rangers execute prisoners, burn ranches, and drive families from their land. The violence is not incidental but institutional—conducted by state officers acting under color of law, often in coordination with local ranchers seeking to acquire Mexican-owned land.
The 1919 Canales investigation by the Texas legislature documents extensive Ranger atrocities but produces only minimal reform: the force is reduced from approximately 1,000 to 76 members, but no Rangers face criminal prosecution for killings during La Matanza. The investigation reveals that Rangers routinely listed Mexican victims as "bandits" killed while resisting arrest, a reporting practice that masks the true scale of the violence. The personnel and practices of the Texas Rangers during La Matanza flow directly into the U.S. Border Patrol when it is founded in 1924—former Rangers constitute a significant portion of the new agency's initial workforce, carrying their methods of collective ethnic punishment into a federal institution.