The US Dept. of Justice's Bureau of Justice Statistics reports that at yearend 2018 there were 1,249,700 sentenced people in state prisons in the US, of whom 176,300 (14.1%) had as their most serious offense a drug charge: 46,500 for drug possession (3.7%) and 129,900 for "other" drug offenses, including manufacturing and sale (10.4%).
E. Ann Carson, PhD. Prisoners In 2019. Washington, DC: US Dept of Justice Bureau of Justice Statistics, October 2020, NCJ255155.