According to the federal Bureau of Justice Statistics:
Of the 3,539,950 adults in the US on probation as of 12/31/2018:
• 75% were male and 25% were female.
• 56% were White non-Latino, 30% were Black non-Latino, 13% were Latino, 1% were American Indian/Alaska Native, 1% were Asian, less than one percent were Native Hawaiian/other Pacific Islander, and less than one percent were two or more races.
• Drug offenses were the most serious offenses for 26% of all people on probation in 2018.

Of the 877,953 adults in the US on parole as of 12/31/2018:
• 87% were male and 13% were female.
• 46% were White non-Latino, 37% were Black non-Latino, 15% were Latino, 1% were American Indian/Alaska Native, 1% were Asian, less than one percent were Native Hawaiian/Other Pacific Islander, and less than one percent were two or more races.
• Drug offenses were the most serious offense for 30% of all people on parole in 2018.

Source

Danielle Kaeble and Mariel Alper, PhD. Probation and Parole in the United States, 2017-2018. Washington, DC: US Dept of Justice Bureau of Justice Statistics, August 2020. NCJ252072.