Could a salary history ban (SHB) reduce the gender wage gap? Proponents of this intervention believe the gap is sustained by the practice of eliciting salary histories from job applicants. Although observational studies suggest that SHB operates as envisioned, two features complicate the interpretation of its effects. These are, respectively, the passage of relevant legislation alongside SHB, and the presence of public campaigns that propel SHB into law. We assessed SHB in the United Kingdom, where neither potential confound was present, and found no evidence that the intervention operated as intended. An intention-to-treat analysis of a 16-month field experiment, conducted with 230 staff at a private educational institution, indicates that SHB was about as likely to harm new hires as it was to help them. Additional analyses did not reveal significant gender differences. We supplement these results with an interrupted time series analysis of placement data from a recruitment firm that voluntarily adopted SHB for its job candidates. Salaries were significantly lower under SHB, but we did not observe gender differences in these data. Taken together, our results suggest that SHB was ineffective in isolation from contemporaneous legislative changes, pro-equality messaging, or some combination thereof.