From The Sentencing Project:

States show significant variation in their use of private prisons. Montana held almost half of its prison population in private facilities, while 23 states did not employ any for-profit prisons.
Since 2000, the federal Bureau of Prisons reliance on private facilities has increased by 39%. The number of people in federal custody in its private facilities totaled 21,565 people in 2021.
Among the immigrant detention population, a daily average of 19,254 people – 79% of the detained population – were confined in privately run facilities in 2021.
The public debate about the causes and consequences of mass incarceration often evokes the ramifications of the private prison movement. While the conditions in these facilities and accusations that the industry perpetuates more incarceration are well documented, the number of people in these prisons is dwarfed by the overall prison population and the harm caused by imprisonment generally.