Immigration law has long labeled certain categories of immigrants “undesirable.” One of the longest-standing of these categories is women who sell sex. Current immigration laws subject sellers of sex to an inconsistent array of harsh immigration penalties, including bars to entry to the United States as well as mandatory detention and removal. A historical review of prostitution-related immigration laws reveals troubling origins. Grounded in turn-of-the-twentieth-century morality, these laws singled out female sellers of sex as immoral and as threats to American marriages and families. Indeed, the first such law specifically targeted Asian women as threats to the moral fabric of the United States due to their perceived sexual deviance. Subsequent laws built upon these problematic foundations, largely without reexamining the initial goal of safeguarding American morality from the ostensible sexual threat of noncitizen women. This dark history casts a long shadow, and current laws remain rooted in these archaic notions of morality by continuing to focus penalties on sellers of sex (who tend to be women), without reciprocal penalties for buyers (who tend to be men). Contemporary societal views on sellers of sex have changed, however, as society has come to increasingly tolerate and accept sexual conduct outside the bounds of marriage. Although societal views surrounding prostitution remain complex, there is an increased understanding of the different motivations of sellers of sex, as well as a recognition that individuals forced into prostitution are victims who need protection. Prostitution-related immigration laws should be reformed to no longer penalize sellers of sex, both to bring immigration law in line with modern attitudes towards sellers of sex and to mitigate the discriminatory effect of the archaic and gendered moral underpinnings that initially gave rise to and continue to show in these laws.