In 1921, Anton Baumstark delivered two lectures on the development of the Roman Rite to a gathering at the Abbey of Maria Laach. Abbot Ildefons Herwegen offered to publish those lectures, but Baumstark decided to write a book on the topic instead, which was published two years later as On the Historical Development of the Liturgy. It would be another sixteen years before he produced Comparative Liturgy, for which he is better known. Together the two books lay out Baumstark's liturgical methodology. Comparative Liturgy presents his method; On the Historical Development of the Liturgy offers his model. For nearly a century, On the Historical Development of the Liturgy has been valued by specialists in the field of liturgical studies, both for its description of comparative liturgy and for the portrayal of patterns Baumstark discerns in liturgical development. Also significant are the hypotheses Baumstark proposes and the evidence he brings to bear on problems in liturgical history. In this annotated edition, Fritz West provides the first English translation of this work by Anton Baumstark.