Scholars and church leaders have recognized Cardinal James Gibbons (1834−1921), archbishop of Baltimore, as a prominent voice for American Catholics. However, few are aware that early sex educators claimed Gibbons as one of their own. Starting in 1912, several national organizations dedicated to sex education elected him as honorary vice president. He was a symbol for the sex education movement, a symbol that gained momentum over time and transformed him posthumously into a founder of sex education. Reasons why are not immediately apparent. To make sense of these representations, it is necessary to understand the historical role of religion in sex education. The embrace of Gibbons grew out of the movement’s liberal Protestant roots and its search for moral legitimacy in a culture that deemed sexual discourse obscene. Gibbons’ reputation grew stronger among sex educators as they sought wider religious support for public campaigns, moving in the direction of ecumenical and interfaith cooperation. His association with these organizations sheds light on the diversity of American Catholic views on sex education—especially in its early days when the mainstream movement did not endorse birth control.