From the plaque:
Our Lady of Guadalupe Church Mission Chapel was established in 1953 by a Spanish-speaking community of Catholic faithful led by Father Donald McDonnell, a member of the San Francisco Archdiocese's "Spanish Mission Band." Here, Father McDonnell befriended a young Cesar Chavez and introduced him to a universe of writings about spirituality, labor rights, human rights, and social justice. Father McDonnell also introduced Chavez to Fred Ross, and the chapel became an important home for their work with the community service organization. Later renamed McDonnell Hall, Guadalupe Mission Chapel provided a foundation for Chavez's work with Dolores Huerta to co-found the United Farm Workers Union and maintains its historic association with Chavez, the UFW, immigrants, and all who are poor in spirit.