ABSTRACT
Government mandated blackouts precipitated a crisis in the optical consciousness of the American public in the first years of the Second World War. In an effort to foil potential aerial bombardment, citizens were asked to turn off their lights and so break an otherwise unqualified promise of modernization: ubiquitous illumination. After decades of constantly increasing levels of artificial light, blackouts challenged not only nighttime visibility, but spatial perception more generally. Americans discussed ways to adjust to dimmer surroundings, to infer spatial information from non-visual senses and familiarize themselves with nightscapes based on specular rather than geometric properties of surfaces. Although the blackouts lasted only a few years in the USA, they reveal the profile, albeit in negative terms, of how the nation's visual environment was imagined around 1940.