Few construction materials have become as ubiquitous as gypsum wallboard. Easily cut, shaped, and transported, its density and mineral nature make it an ideal solution to interior issues of fire separation, acoustic privacy, and durability. Meanwhile, the abundance of gypsum throughout the world and efficient manufacturing processes have made it affordable for virtually all building types. Yet, like many building materials of the last century, gypsum wallboard’s history belies its commonplace usage today. It was among the 20th century’s most disruptive technologies in terms of construction labor, threatening the livelihoods of tens of thousands of tradespeople and radically altering the pace and staffing of traditional interior jobs. Wallboard’s introduction forced city building commissions to directly address the growing impact of industrialization on American construction in the postwar era and the simultaneous waning influence of labor unions. It was a signal moment in the industrialization of construction, altering expectations for interior finishes and detail while influencing the wholesale evolution of building codes from prescriptive models to performance standards. Gypsum wallboard also helped to spawn a new laboratory testing industry that, in turn, encouraged the further amplification of building science research and development throughout the last half of the 20th century. Wallboard’s effects were particularly impactful in Chicago. This city saw some of its earliest applications, its major corporate producer’s headquarters, and virulent fights over its application and impact on demography and the evolving balance of power among the city’s labor and trade unions.