Two states -- Colorado and Washington -- have legalized marijuana for recreational use. Nineteen other states and the District of Columbia allow some legal use of marijuana, primarily for medicinal purposes.
Note: In Maryland, the use of marijuana for medicinal purposes can be used as a defense in court. However, the state doesn't provide a way for patients to obtain marijuana.
Sources: National Organization for the Reform of Marijuana Laws (NORML); National Conference of State Legislatures (NCSL)