Despite the substantial interest in mass imprisonment, limited research has studied how mass incarceration has occurred across the 3000 city and county jails in the United States. Using Bureau of Justice Statistics surveys and censuses of US jails, we investigate patterns of jail construction over the last 50 years and ask whether these infrastructural changes represent expanding carceral capacity or simply capacity restructuring , whereby jails were consolidated and renovated rather than multiplied. Despite consistent numbers of jails over time, jail populations have increased substantially, suggesting that mass incarceration has functioned differently in jails than in prisons. We posit a theory of “jailization,” whereby jails have permeated the membranes of different arms of the criminal legal system to serve as a catchment center or “lobby,” and argue for dedicated studies of jails’ unique and flexible roles. This contributes to the literature on penal change by showing that changes to jails during the era of mass incarceration look markedly different than that of prisons, underscoring the importance of studying them as unique criminal legal institutions.
Friday et al. (2026) studied this question.