Book and Key was a Swarthmore College men's secret honor society established circa 1906 and modeled after the secret societies at Yale University. The group was organized by Morris L. Clothier (Swarthmore '90), Howard Cooper Johnson (Swarthmore '96) and Dr. Howard Tily. Clothier, president of Strawbridge and Clothier Department Store, financed the group in its early years, paying for the construction of a windowless clubhouse, the Temple on Elm Ave, later sometimes referred to as the Jug. The Temple was completed in 1906, and that same year a select group of seven Swarthmore seniors became the first members of Book and Key.

The society kept a large Bible and oversize key in the Temple which was used in many of the ceremonies, hence Book and Key. Key refers to the key of knowledge.

Throughout its existence Book and Key was financially supported by the Temple Trust Association, an alumni association composed of graduated Book and Key members and the founders. A committee of Temple Trust Association members advised the Book and Key seniors in choosing the following year's members. The Temple Trust Association held the deed for the Elm Ave clubhouse.

The group's rituals and ceremonies revolved around the number seven. The membership was limited to seven male members of the senior class chosen each spring by the previous graduating class. On held the first Thursday each May, the student body would gather by Swarthmore's Parrish Hall, and a member of Book and Key would rush in to the crowd every seven minutes to tap one of the chosen Juniors. The initiation rites were conducted the following Thursday in front of the Temple.

In the early years, members of Book and Key pledged to keep the group's activities secret. While the secrecy gave Book and Key an aura of mystery, in later years, this secrecy made it more vulnerable to criticism. The society didn't publicize its contributions to the college, preferring to remain anonymous. In the early 1930s the group ended Tap Night, and about 1945 decided to expand its membership beyond seven. Gradually, the members of the group began to abandon the tradition of secrecy.

In the 1940s and 1950s in response to growing criticism, Book and Key redefined its role on campus. For most of the period from 1942 to 1955, Book and Key was in charge of freshman orientation. The group also helped usher at commencement ceremonies, visited high schools to promote Swarthmore College, and hosted high school students on overnight visits at the college. Each April, the group co-sponsored with the Little Theater Company a one act play contest. In the 1940s, Book and Key also organized a number of community service projects.

In spite of these reforms, the group remained controversial. Select societies and college traditions were no longer in vogue. In the spring of 1957, Book and Key, with the input of leading members of the Temple Trust Association, debated the group's future. The group was unable to make a decision. A majority of the senior members of the class of 1957 wanted to eliminate the selection process entirely, but were opposed by Book and Key's alumni who generally preferred to see Book and Key dissolve rather than be so radically changed. None of the members of Book and Key of 1957 were inducted into the Temple Trust Association, nor were any members of that year's junior class invited to become members of Book and Key. Book and Key alumni tried to restart the organization on campus, but these attempts failed. At a meeting on May 27, 1965, it was decided to formally dissolve the organization. The Temple Trust Association gave Swarthmore College the deed to the Elm Avenue property. The investment fund was used to begin a Book and Key Scholarship for a graduating senior male. In 1966, after being empty for almost ten years, Book and Key's Temple was demolished.