The legal history of cannabis in the United States began with state-level prohibition in the early 20th century, with the first major federal limitations occurring in 1937. Starting with Oregon in 1973, individual states began to liberalize cannabis laws through decriminalization. In 1996, California became the first state to legalize medical cannabis, sparking a trend that spread to a majority of states by 2016. In 2012, Washington and Colorado became the first states to legalize cannabis for recreational use.