An illegal drug conviction was the most serious offense for 176,300 out of the 1,249,700 people in the US sentenced to and serving time in state prisons at year-end 2018. That represents 14.1% of all sentenced prisoners under state jurisdiction. Of those 176,300 people: 64,500 (36.6%) were non-Latinx white, 52,100 (29.6%) were non-Latinx African American, and 28,800 (16.3%) were Latinx. No race/ethnicity was reported for the remaining 30,900 people (17.5%) serving time in state prison for a drug offense.
(Note: The Bureau of Justice Statistics annual report on prisoners does not provide separate counts for inmates who identify as two or more races, nor of American Indians, Alaska Natives, Asians, Native Hawaiians, or other Pacific Islanders.)

Source

E. Ann Carson, PhD. Prisoners In 2019. Washington, DC: US Dept of Justice Bureau of Justice Statistics, October 2020, NCJ255155.