During the Second Industrial Revolution, in the late nineteenth century, the proliferation of automation technologies coincided with substantial job creation but also a “hollowing out” of middle-skilled job opportunities, which historically offered reliable paths to prosperity. We use recently linked U.S. census data to document three main facts: (i) declining demand for middle-skilled labor in manufacturing corresponded to greater reallocation of workers into comparatively less-skilled occupations; (ii) older workers were more likely to switch to unskilled physical labor; (iii) younger workers led switching into growing occupations affected by automation technologies.