Public attitudes towards weed have softened so quickly that anti-marijuana activists are starting to look like historical anachronisms.

While the radical change in public attitudes toward marijuana has been swift, it also hasn't been overnight. This animated map shows how it took decades of effort — and a major push from below by younger Generation X and millennial voters — to change state laws, and people's minds, on marijuana legalization in the United States:

David Mendoza/Mic

As the chart shows, some of the states now legalizing medical or recreational marijuana actually first decriminalized pot 30 years or more ago. Attitudes towards marijuana were somewhat looser than during the mid-1980s to early '90s, when, the Baker Institute's Katharine Neill argues, "politicians and the media portrayed the crack epidemic as a plague of the urban ghetto that threatened to ravage the suburbs."

Lifting the U.S. out of the hole it dug during the war on drugs has taken grueling state-by-state efforts. Just a handful of West Coast states (Washington, Alaska, Oregon and Colorado) have actually legalized recreational weed. Meanwhile, the U.S. is still deeply committed to police and military approaches to the drug trade many experts believe are hopeless.

Now the pendulum has swung towards legalization, but this time, it doesn't seem likely to swing back.

The past decade has seen support rise to 68% of millennials, 52% of Generation X and 50% of the Baby Boomers in 2015. Only the Silent Generation, those born in the mid-1920s to early 1940s, remain resolutely opposed to marijuana legalization, and states where no reform has been passed at all tend to be in the South and Midwest.