A new Gallup poll finds 60 percent of American adults believe marijuana should be legal. A recent study released by the Pew Research Center found 57 percent of U.S. adults say they support legalizing marijuana. In 1969, only 12 percent of Americans supported marijuana legalization, according to Gallup. Support for legalization has risen among almost every demographic group in the past decade, according to The Washington Post . Almost 80 percent of young adults ages 18 to 34 favor legalization, up from 44 percent in 2005. Five states—California, Arizona, Massachusetts, Maine and Nevada—will vote on marijuana legalization in November. Marijuana is legal for personal use in Colorado, Washington, Oregon, Alaska and the District of Columbia.