California has become the largest American state to legalize the sale of marijuana. The new law took effect on New Year’s Day. California voters approved a measure to legalize the drug in November 2016. The law permits adults, 21 years and older, to possess as much as 28 grams of marijuana. It also permits people to grow up to six marijuana plants at home. California is the sixth U.S. state, along with the nation’s capital Washington D.C., to legalize recreational marijuana. California became the first American state to approve marijuana use for medical purposes in 1996. At least 29 U.S. states now permit the use of medical marijuana. Maine and Massachusetts are expected to legalize recreational marijuana in 2018.