Women, on the whole, fared even worse. “Policy makers operated on the assumption that the primary function of unemployment insurance was to replace the wages of male breadwinners, who were understood to earn a ‘family wage,’ ” Professor Mettler writes. Most women who worked were in intermittent or part-time jobs that didn’t qualify, nor did they make enough to meet the thresholds. Those who left work because of home obligations, such as raising children, were deemed to have left “voluntarily” and were ineligible.

The Fair Labor Standards Act of 1938, which for the first time created a floor under wages and a roof over hours, ensuring that people weren’t worked to death for a pittance, again excluded farmworkers and maids. Domestic workers weren’t added until 1974, and only last year did home health aides get the same treatment.

Unionization created another economic foothold — but that, too, was mostly available to white men. The National Labor Relations Act enshrined a number of labor rights that significantly increased the movement: While just four million Americans were union members in 1929, by 1948 that reached 14.2 million. But the N.L.R.A. excluded agricultural and domestic workers. Women made up less than one-tenth of union members through 1940.

Perhaps no program was as important in creating the middle class of the 1950s and ’60s, though, as the G.I. Bill. The government spent more than $95 billion on it between 1944 and 1971, and millions of people used its benefits to buy homes, go to college, start businesses and find jobs. Women could get benefits if they served, but they made up just 400,000 out of the more than 16 million people who served during World War II.

Black men enlisted in great numbers; more than 900,000 of those who served in the war were African-American. And once they returned home, many of them applied for G.I. benefits. This time there were no formal exclusions. But the government handed implementation of the veterans’ programs down to states and localities, including those in the grips of Jim Crow.

Black veterans’ applications for business assistance were routinely denied. Those seeking a college education were crowded into limited slots in segregated institutions. Even though the mortgages were guaranteed, black borrowers had to get a bank to lend to them, and most refused. In the suburbs of New York and New Jersey, less than 100 of the 67,000 G.I. Bill-insured mortgages were for nonwhites. “The G.I. Bill did create a more middle-class society, but almost exclusively for whites,” Professor Katznelson writes.