By the time it was released, a group within the Reform movement led by Rabbi David Einhorn of Baltimore sought to implement greater changes, and the 1892 editions were recalled at significant cost.
[1] At a meeting of American and Canadian Reform leaders held in Toronto in June 1966, an announcement was made that the CCAR's Committee on Liturgy would begin a "re-evaluation and research" process aimed at a rewrite of the Union Prayer Book[5] At the 78th annual meeting of the CCAR in June 1967, held at The Ambassador Hotel in Los Angeles, discussions were undertaken regarding a replacement or revision of the Union Prayer Book.
Rabbi Joseph Narot, who had been working on the project, described how the Union Prayer Book had been last updated 30 years prior, "before the Nazi holocaust, before the atomic bomb and before the space age" and that it did not address "the theological and moral questions that have been raised by these momentous issues".
[6] With rising interest in the 1960s in Zionism and The Holocaust, as well as an upsurge in Jewish pride and identity following the Six-Day War, it became clear that the Union Prayer Book was no longer adequate.
Only a handful of ultra-liberal congregations have adopted the Sinai Edition of the UPB, the rest preferring to use Gates of Prayer or Mishkan Tefillah, which reflect more closely the neo-traditionalist trends in the Reform Movement.