The Casasola Archive contains photographs of Mexico from 1900 to 1970 , and offers a look that covers the last years of the nineteenth century. The Casasola collection contains positive and negative films , in different formats and on various photographic media . Since 1976 , is kept in the heated rooms of the National Photographic Library , the National Institute of Anthropology and History ( INAH ) in Pachuca , Hidalgo, Mexico , in the former Franciscan convent , now a cultural center. The work of the photo library is to ensure the conservation and cataloging of photographic heritage . Photo library currently comprises 39 funds , with a total of 850 000 pieces (positive and negative ) .