By Sarah Dutton, Jennifer De Pinto, Anthony Salvanto and Fred Backus

For the first time since the CBS News Poll began asking the question, a slight majority of Americans favor the legalization of marijuana use.

Fifty-one percent say they think the use of marijuana should be made legal, while 44 percent do not. Public opinion on this issue has changed dramatically over the past few years: in October 2011 a slight majority (51 percent) opposed making marijuana use legal, and as recently as April 2013 public opinion was divided on this issue (45 percent supported, 45 percent opposed). Interestingly, in July 1979, when CBS News first asked the question, 69 percent thought marijuana use should not be made legal and only 27 percent thought it should be made legal.

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Making Marijuana Legal: The Demographics

Views that marijuana use should be made legal have risen across nearly every demographic group since April 2013:

Support for legalizing marijuana use has grown among Americans under 44, and now most Americans 45 to 64 think marijuana should be legal (55 percent; in April this age group was divided). The only age group that still opposes legalizing marijuana use is seniors 65 and older.

Support has increased among both men and women, but there remains a gender gap. Most men (57 percent) think marijuana use should be made legal, while fewer women (46 percent) think so.

Most Democrats (59 percent), independents (54 percent), liberals (72 percent), and moderates (54 percent), support legalizing marijuana use.

However, most Republicans (61 percent) and conservatives (61 percent) oppose legalizing marijuana, though support has risen among these groups as well.

Support for legalizing marijuana use has risen six points among Americans earning under $100K a year (50 percent now vs. 44 percent), and 12 points among those earning $100K or more (64 percent now vs. 52 percent).

Medical Marijuana

Americans support the use of marijuana for medicinal purposes in overwhelming numbers. Eighty-six percent think doctors should be allowed to prescribe small amounts of marijuana for patients suffering from serious illnesses. Americans have supported medical marijuana use since 1997 when CBS News began asking the question, though then 62 percent thought doctors should be allowed to prescribe marijuana for medical use.

Still, a majority of Americans show some skepticism about the medical marijuana programs that exist today. Just a third of Americans think most of the marijuana that is being purchased in this country through state authorized programs is being used to alleviate suffering from serious medical illnesses. Most – 56 percent - think it is being used for other reasons.

Nevertheless, 77 percent of Americans who think most of the medical marijuana purchased is being used for other purposes still think doctors should be allowed to prescribe medical marijuana.

Who Should Decide: Federal Gov't or States?

Marijuana use remains illegal under federal law, though a majority of Americans don’t think this is a matter that should involve the federal government. Sixty-two percent say legalizing marijuana should be left up to each state government to decide.

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This poll was conducted by telephone January 17-21, 2014 among 1,018 adults nationwide. Data collection was conducted on behalf of CBS News by Social Science Research Solutions of Media, Pa. Phone numbers were dialed from samples of both standard land-line and cell phones. The error due to sampling for results based on the entire sample could be plus or minus three percentage points. The error for subgroups may be higher. Interviews were conducted in English and Spanish. This poll release conforms to the Standards of Disclosure of the National Council on Public Polls.