For most of the twentieth century, the official United States definition of rape—"the carnal knowledge of a female forcibly and against her will"—rendered most sexual victimization invisible to law, crime statistics, and epidemiology. This review traces the evolution of legal definitions, measurement technologies, reporting behavior, and epidemiological knowledge of sexual assault in the United States from 1900 through 2026, synthesizing legal history, survey methodology, national and campus prevalence studies, and meta-analytic evidence on consequences. Three revolutions define this history. First, statutory reform between the 1970s and 1990s abolished corroboration and resistance requirements, enacted rape shield protections, and made sexual assault laws gender neutral. Second, the federal statistical definition was revised in 2012-2013 to a gender-neutral, consent-based penetration standard, immediately raising officially recorded counts by more than a third. Third, behaviorally specific measurement—pioneered in the late 1970s and validated in 1987—showed that prevalence estimates from such instruments exceed those from crime-survey questions by four- to eleven-fold. Contemporary surveillance places lifetime attempted or completed rape at 18.3% of United States women and 1.4% of men, concentrated in adolescence and young adulthood and overwhelmingly unreported. Reporting research reveals persistent rape myths and negative institutional reactions as filters that suppress counts and compound harm, while intersectional and life-course analyses show exposure and consequence stratified by race, disability, gender identity, sexual orientation, and cumulative adversity. The history of sexual assault in the United States is largely the history of its definitions and instruments; unresolved issues of harmonization, inclusivity, and standardization define the methodological agenda ahead.