WASHINGTON, D.C. (WTVN) -- Support for the legalization of marijuana has spiked in the last 12 months, according to a Gallup poll. It found that 58 percent of Americans now think the drug should be legal. That's a sharp contrast to the time Gallup first asked the question in 1969, when only 12 percent favored legalization.

Public support for legalization more than doubled in the 1970s, growing to 28 percent. It then plateaued during the 1980s and 1990s before inching steadily higher since 2000, reaching 50 percent in 2011.

38 percent of Americans also admitted to having tried the drug.

"As the laws are becoming more progressive throughout the country and it's becoming a more accepted thing you're just having more people come out for it," said Michael Rivercomb with the Ohio Chapter of the National Organization for the Reform of Marijuana Laws.

Success at the ballot box in the past year in Colorado and Washington may have increased Americans' tolerance for marijuana legalization. Support for legalization has jumped 10 percentage points since last November and the legal momentum shows no sign of slowing down. Last week, California's second-highest elected official, Lt. Gov. Gavin Newsom, said that pot should be legal in the Golden State, and advocates of legalization are poised to introduce a statewide referendum in 2014 to legalize the drug.

There's also a push to get marijuana legal in Ohio. Supporters are also trying to get medical and industrial use of cannabis legalized.

The movement to legalize marijuana mirrors the relatively recent success of the movement to legalize gay marriage, which voters have also approved now in 14 states. Public support for gay marriage, which Americans also overwhelmingly opposed in the past, has increased dramatically, reaching majority support in the last two years.

The jump in support for legalization has occurred largely among independents, 50% of whom were in favor last year. In 2013, however, that number increased by double digits to 62%. Support for legalization among Democrats and Republicans saw little change. Yet there is a marked divide between Republicans, who still oppose legalizing marijuana, and Democrats and independents.

"We just don't need the government telling us what to do unless it's absolutely necessary," Rivercomb said.

Americans 65 and older are the only age group that still opposes legalizing marijuana. Still, support among this group has jumped 14 percentage points since 2011.

In contrast, 67% of Americans aged 18 to 29 back legalization. Clear majorities of Americans aged 30 to 64 also favor legalization.

The increasing prevalence of medical marijuana as a socially acceptable way to alleviate symptoms of diseases such as arthritis, and as a way to mitigate side effects of chemotherapy, may have also contributed to Americans' growing support.

Opponents, such as law enforcement and substance abuse professionals,have cited health risks including an increased heart rate, and respiratory and memory problems.

"It's certainly not good public health policy to have marijuana or any other addictive drug become legalized in the United States," said Marcie Siedel with the Drug Free Action Alliance.

She says young people are especially impacted and are being bombarded with pro-marijuana messages in their music, in movies, and on television. She admits that pro-marijuana groups have done a better job of getting their message out.