This report from the Vera Institute of Justice provides information collected directly from states and the federal Bureau of Prisons to estimate the number of people in prison at the end of 2017.
"The data revealed that the recent trend of decreasing prison incarceration continued in 2017, with the total U.S. prison population dropping below 1.5 million for the first time since 2004. Despite the overall declines, 20 states increased their prison population, leaving 10 states with all-time-high numbers of people in prison."
