Vol. 125 No. 6 This Article argues that the “traditional concept” of sex discrimination is an invented tradition. It purports to reflect the historical record, but in fact reflects normative judgments about how deeply the law should intervene in the sex-based regulation of the workplace. Recovering the largely forgotten legislative history of Title VII’s sex provision, this Article shows that there was little consensus and much debate in the 1960s about what qualified as sex discrimination. Employers advanced the argument that Title VII applied only to practices that sorted men and women into two perfectly sex-differentiated groups in order to preserve the traditional gendered organization of the workplace and insulate particular employment practices from scrutiny. In the 1970s, courts adopted this interpretation but no longer cited the need to preserve conventional sex and family roles as a justification; instead, courts cited deference to the legislature and fidelity to tradition as justifications for interpreting the law narrowly. This Article shows that history does not compel courts to interpret Title VII’s prohibition of sex discrimination in anticlassificationist terms – and that, in fact, in cases where anticlassificationism produces expansive rather than narrow results, courts have routinely departed from it.