Prevalence of Marijuana Use among People in the US Aged 12 or Older

In 2015:
an estimated 117,865,000 people aged 12 or older in the US had tried marijuana at least once in their lifetimes.
an estimated 36,043,000 people aged 12 or older in the US had tried marijuana at least once in the past year.
an estimated 22,226,000 people aged 12 or older in the US had tried marijuana at least once in the past month.

Table: Marijuana Use in Lifetime, Past Year, and Past Month among Persons in the US Aged 12 or Older, by Demographic Characteristics: Number in Thousands

Source: 

Center for Behavioral Health Statistics and Quality. (2016). 2015 National Survey on Drug Use and Health: Detailed Tables. Substance Abuse and Mental Health Services Administration, Rockville, MD, p. 242, Table 1.33A.