Later, when Martin Marietta’s counsel explained that the assembly-line job denied to Phillips was not “heavy work” but rather “intricate work” involving “small electronic components,” Burger stated that that was surely why women comprised the bulk of the company’s workforce. “[W]omen are manually much more adept than men and they do this work better,” he opined, adding, “Just the same reason that most men hire women as their secretaries, because they are better at it than men.”

That the Chief Justice of the Supreme Court apparently had no qualms about declaring women to be inherently better secretaries than men spoke volumes about how little Title VII had done in its six-year existence to uproot, or at least to stigmatize, the cultural biases motivating a lot of sex discrimination.

Shortly after the oral argument, the Court issued its unanimous decision. Like so many Court rulings, it was a mixed bag. In one sense, it was a big win for Ida Phillips, and for all employees covered by Title VII: The Court agreed that refusing to hire mothers (or any other sub-group of protected workers) was just as discriminatory as if Martin Marietta had refused to hire any women at all. That expansive definition of Title VII’s coverage still stands. But the Court apparently agreed that Martin Marietta’s concerns about mothers’ job commitment weren’t off-base; it sent the case back to the lower court for a trial, so the company could present any evidence it could muster that mothers in fact had higher rates of absenteeism, or made more mistakes, or took more phone calls during the work day, than non-mothers. Title VII allows employers this loophole. If they can prove that only one sex could do a certain job—say, that only a woman could portray Cleopatra in a stage production—then it isn’t illegal to restrict that job to men only or women only. Notably, the law doesn’t permit this exception for race discrimination, preventing employers from ever deeming certain jobs “for whites only” or “for blacks only.”

As it turned out, Martin Marietta had no appetite for a trial, and settled Ida Phillips’s case soon after. (She used the modest proceeds to give her daughter a down payment on a house, buy herself the first air conditioner she’d ever had, and take her youngest daughter—the one who had cost her the job at the company—to Disneyworld.) And subsequent court decisions have departed from the Supreme Court’s interpretation of Title VII’s loophole; its willingness to give Martin Marietta a chance to use a stereotype to justify discrimination against all mothers has not, for the most part, prevailed.

The reality, though, is that motherhood continues to pose a stubborn barrier to working women. When Phillips applied to work on that assembly line, only about 25 percent of mothers with children under six were in the workforce. Today, that number has more than doubled, to nearly 70 percent. Yet studies confirm that mothers are still viewed as less committed to their jobs than men. This “maternal wall” results in lower pay for mothers than for fathers, fewer opportunities for advancement, and even—just as Ida Phillips faced—outright job denial. True, the biases on display at that oral argument 45 years ago may not be voiced as openly or as often, because thanks to Title VII, they’re recognized as illegal. But make no mistake: They’re still there.

The sub-headline to this article originally stated that Phillips v. Martin Marietta Corporation was decided 50 years ago. We regret the error.