"On December 31, 2018, an estimated 2,123,100 persons were either under the jurisdiction of state or federal prisons or in the custody of local jails, which was 30,500 fewer persons than in 2017. By year-end 2018, the number of persons incarcerated in state or federal prisons or local jails fell to the lowest level since 2003, when 2,086,500 persons were incarcerated (not shown in tables).
"During 2018, the prison population decreased 1.6%, while the jail population remained relatively stable. The prison population at year-end 2018 (1,465,200) was at its lowest level since 2002 (1,440,100; not shown in tables). The total incarcerated population was 1.4% lower in 2018 than in 2017."
Laura M. Maruschak and Todd D. Minton. Correctional Populations in the United States, 2017-2018. Bureau of Justice Statistics: Washington, DC. August 2020. NCJ252157.