As I’ve been foraging through the history of inaugural prayers, one question has remained a mystery: why, in 1937, did Franklin Roosevelt start the tradition?
Professor Mark Silk has come up with an interesting and plausible theory.
Prior to 1937, the vice presidents were sworn in by their predecessor in the Senate chamber. A prayer was said after the swearing in. Roosevelt decided to have the vice presidential swearing in be part of the main event. Not wanting to deprive the Senate chaplain of his prayer role, he moved to the big stage too.

In addition, Silk argues, Roosevelt undoubtedly saw a political opportunity so he created a second clergy slot and gave it to Msgr. John A. Ryan — who was a major Catholic supporter of the New Deal.
Read Silk’s full theory and description of Ryan’s fascinating role as a FDR ally.