In the late seventeenth century, General Alonso de León led five military expeditions from northern New Spain into what is now Texas in search of French intruders who had settled on lands claimed by the Spanish crown. Lola Orellano Norris has identified sixteen manuscript copies of de León’s meticulously kept expedition diaries. These documents hold major importance for early Texas scholarship. Some of these early manuscripts have been known to historians, but never before have all sixteen manuscripts been studied. In this interdisciplinary study, Norris transcribes, translates, and analyzes the diaries from two different perspectives. The historical analysis reveals that frequent misinterpretations of the Spanish source documents have led to substantial factual errors that have persisted in historical interpretation for more than a century. General Alonso de León’s Expeditions into Texas is the first presentation of these important early documents and provides new vistas on Spanish Texas.