Primeros Memoriales, by Fray Bernardino de Sahagún, is a valuable document providing great understanding and knowledge of provincial Mesoamerican civilization. In 1558 the Spanish Franciscan missionary Fray Bernardino de Sahagún was commissioned by the Catholic Church to conduct a systematic investigation of the indigenous culture, particularly the religious/ritual system, the dominant native language of Central Mexico, Sahagún worked with trilingual (Nahuatl/Spanish/Latin) Indian assistants between 1559 and 1561 to produce what came to be known as the Primeros Memoriales. Although it originally was intended to facilitate the proselytizing efforts of the Church, this priceless document by the "father of modern ethnography" contributes more significantly than any other single project to our knowledge and understanding of provincial Mesoamerican civilization. Sahagún chose Tepepolco, a large town northeast of Mexico City, as the site of his study; there he interrogated a group of elderly, upper-class informants. The result was explanations, written Nahuatl by his assistants. The first stage of Sahagún?s monumental Historia General de las Cosas de Nueva Espana, the Primeros Memoriales is a significant document in its own right. Less than 10 percent of the written data and virtually none of the iconography were incorporated into the Historia General. The Primeros Memoriales is unique, moreover, because it deals with Aztec culture from the point of view of a sizable but provincial Mexican community rather than the urban, aristocratic viewpoint represented in most other documents. The Primeros Memoriales is housed in two repositories in Madrid - the Palacio Real of the Patrimonio Nacional and the Real Academia de la Historia. In 1905 Aztec scholar Francisco del Paso y Troncoso selected 108 pages from the Palacio Real and 68 from the Real Academia that he judged to be the materials Sahagun had assembled in Tepepolco and gave the assembled manuscript the name Primeros Memoriales.