Las Posadas collection contains material relating to the long tradition of Carrillo Elementary School's re-enactment of Mary and Joseph’s pilgrimage from Nazareth to Bethlehem in a procession seeking shelter or posada. This event was based on an old Mexican yuletide custom, adopted by Miss Marguerite Collier in 1937 to build Tucson students’ pride in their Hispanic heritage. It has since then become an annual celebration for all its students and the community.

Included within the collection are artwork and writings, invitations, programs, event history, correspondence, photographs, publications, newspaper clippings related to the event, music books, song lyrics, class lists of participating students, colored slides and compact discs of Carrillo student performances, and a custom designed event t-shirt.