Despite the special role of tenure-track faculty in society, training future researchers, and producing scholarship that drives scientific and technological innovation, the sociodemographic characteristics of the professoriate have never been representative of the general population. Here we systematically investigate the indicators of faculty childhood socioeconomic status and consider how they may limits efforts to diversify the professoriate. Combining national-level data on education, income, and university rankings with a 2017-2020 survey of 7,204 U.S.-based tenure track faculty across eight disciplines in STEM, social science, and the humanities, we show that faculty are up to 25 times more likely to have a parent with a PhD. Moreover, this rate nearly doubles at prestigious universities and is stable across the past 50 years. Our results suggest that the professoriate is, and has remained, accessible disproportionately to the socioeconomically privileged, which is likely to deeply shape their scholarship and their reproduction.