Scroll and Key exists because Skull and Bones once split. In 1842, a group of Yale students broke from Skull and Bones, then already established as the university's most prominent senior society, and founded a rival organisation of their own. That founding-by-schism is unusual among American collegiate secret societies, many of which were founded independently by students with no prior institutional tie to an existing rival, and it set a pattern that shaped the two societies' relationship for the century and a half that followed: parallel structures, comparable prestige, and a rivalry understood by generations of Yale students as running alongside, rather than beneath, whatever genuine friendship individual members of each society might have with each other.
The split also fixed the basic template both societies would follow. Each admits a small cohort of students annually into lifelong membership, each meets in its own dedicated, windowless building on or near campus, referred to by members as a tomb, and each maintains a culture of ritual secrecy about its internal practices that has fuelled outside curiosity for generations, curiosity Skull and Bones has attracted rather more of, given its later association with prominent American political families. Scroll and Key's own membership rolls include a comparable roster of graduates who went on to notable careers, even if the society has drawn less sustained public attention than the rival it split from at its founding.