The late 1940s and 1950s are rightly regarded as a period of social upheaval and restructuring on both sides of Atlantic. The post-war Baby Boom, the GI Bill, the Cold War, suburbanization, growing prosperity, urban regeneration, social mobility, road building, and car and television ownership all form part of this story. These years are also often viewed in retrospect as a ‘boom time’ for mainstream religion: a time of growing devotion, church building, and—among Catholics particularly—growing self-confidence and social acceptance. Yet under the surface, cracks were beginning to form, with lapsation (or leakage) a source of growing anxiety. This chapter narrates the socio-religious history of this period, in light of three theoretical lenses: social network theory, plausibility structures, and Credibility Enhancing Displays (CREDs).