CNN linked to an All Saints Day fact sheet published by the University listing facts prepared by Rev. Michael Witczak, associate professor, liturgical studies.
... Pope Gregory III built and dedicated a special chapel in Rome in the 8th century in memory of all the saints on November 1, according to the Catholic University of America. Then Pope Gregory IV and Emperor Louis the Pious extended the November 1 feast of All Saints to the Holy Roman Empire in the 9th century, and from there it spread throughout Europe. ...
Continue reading at CNN.