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Although many states’ policies and laws concerning marijuana use have recently become more permissive, little is known about the impact of recreational marijuana legalization (RML) on rates of use, risk factors associated with use, and patterns of use over time. We compared samples from 2 longitudinal studies focused on understanding risk and protective factors related to substance use from adolescence to young adulthood (N = 1,468). The samples were collected 10 years apart from the same neighborhoods in an urban area, and the same measures, research design, and data collection procedures were used in each study. As such, the samples are matched on many demographic variables and provide a unique opportunity to compare rates of use and other associated risk factors before and after RML in Oregon. Our results suggest increased marijuana use in a 30-day time frame among Sample 2 during the young adult years, the time at which RML went into effect in Oregon. In Sample 2, young adults had 2.12 times the odds in Sample 1 of using marijuana at age 24, and they were more likely than those in Sample 1 to report use over multiple time points in young adulthood. Overall, our results suggest that young adults after RML are more likely to use marijuana than young adults were before RML 10 years earlier. Implications for prevention and education are discussed in light of rising rates of daily and 30-day use patterns among this population.