This article provides an overview of gender inequality in labor markets in the United States. I show trends in labor force participation, occupational segregation, and the pay gap. Though my main focus is the United States, I note where similar findings exist for other affluent nations. I explain what we know from past research about the causes of inequality and note the gaps in our knowledge. In broad brush strokes, the sex gap in pay in the United States has two major sources: the segregation of jobs and the effects of women's responsibility for childrearing. My major thesis is that at least in the United States, these two are largely unrelated. That is, the causes of segregation do not seem to be largely about women's mothering responsibilities, and the penalties for motherhood do not appear to flow largely through segregation. This thesis is at odds with much thinking among economists, who have seen segregation as a rational response by employers and employees to gender differences in intermittence of employment. In this economic view, women choose more "mother-friendly" jobs, which maximize their earnings conditional on intermittent and flexible employment but tradeoff on-the-job training, higher earnings, and steeper wage trajectories to do so.