Abstract: This dissertation charts the rise in importance of religious identities in American life during the nineteen-forties, nineteen-fifties, and early nineteen-sixties. One of the dissertation's central goals is simply to show how important it was during these years to possess an identity associated with being Catholic or being Jewish. After tracing distinctions between Protestants, Catholics, and Jews in several arenas (college-level fraternities, education, popular culture, and housing), this dissertation makes plain the fact that during the immediate postwar years religion was rightfully treated as a social marker almost as significant as race. This fact is generally missing in our historiography. Beyond asserting the importance of religious identities in postwar America, this dissertation also demonstrates that postwar Catholics and Jews often resisted the temptation of assimilation, choosing instead to fight for a version of pluralism. Rather than meekly accept the crumbs mainstream society was willing to toss them as they gave up mare and more of what made them unique, postwar Catholics and Jews chose instead to retain much of their distinctiveness. By the nineteen-fifties it was clear that postwar Catholics and Jews were seeking access and acceptance without always seeking assimilation. In doing so, they provoked a sharp dialogue about the proper ideological make-up of the American nation. Should Catholics or Jews have to give up facets of their belief just to earn acceptance? Shouldn't mainstream society honor them by altering common practices that were offensive to Catholics and Jews? In the end, Catholics and Jews argued that what had to be changed was society itself, not the groups that were part of it. This represented something new in American life. Challenging the prevailing melting pot ideal, postwar Catholics and Jews developed a defense of group identities that set the stage for the dialogue on diversity that was to unfold over the remainder of the twentieth century (and that continues today). In showing this, this dissertation challenges much of our historiography, which typically locates the origins of pluralism in the latter part of the Civil Rights Movement.