marijuana
Reuters
It has been six months since Colorado and Washington voted to legalize marijuana, and the momentum for changing the way states handle pot has never been stronger. 
May was a huge month for marijuana reform supporters, with a string of significant wins and important milestones as more and more states lean toward a laissez-faire approach to marijuana. 
First and foremost, the Colorado Legislature successfully navigated its first big regulatory test, inventing the legal framework for a marijuana economy.
House Bill 1317 was the law that resulted from Amendment 64, the ballot initiative that legalized pot, dictating that Coloradans can buy an ounce of pot from specially licensed stores. House Bill 1318 set up the tax infrastructure for the market, which will go up for voter referendum in November. 
Gov. John Hickenlooper is set to sign both bills today, according to KDVR.
There's also been significant movement in other states in pursuing a similar system. May saw the NYPD's arrest numbers for marijuana offenses begin to decline, Christopher Robbins at Gothamist reported, with Commissioner Ray Kelly pushing pot to the back seat in favor of drugs that have dangerous effects. 
New York City arrests for marijuana possession are set to drop 20% in 2013.
Upstate in Albany, State Senator Liz Krueger swore to introduce a law to decriminalize, regulate, and tax marijuana in New York State, Dana Rubenstein at Capital New York reported.
The Empire State has been floated as one which could be in the next batch of states that, like Colorado and Washington, have a legal marijuana economy. 
On the West Coast, incoming Los Angeles Mayor Eric Garcetti indicated Monday he supports legalizing marijuana for general use. This comes a month after California Lieutenant Governor — and potential 2014 gubernatorial candidate — Gavin Newsom penned an op-ed calling for California to legalize pot. 
Most interesting of all is movement in Illinois to approve medical marijuana. The bill passed the state Senate earlier this month and awaits Gov. Pat Quinn's signature. 
On the whole, the political success for marijuana in May is really just the implementation of American's changing views on pot.
A Reason-Rupe poll from earlier this month found that a mere 6% of Americans think marijuana possession should be punished with jail time. This, combined with a new majority of Americans supporting legalization, has dealt a devastating blow to opponents of legalization.