The United States is gradually becoming the land of the red, white, and green.

After a historic election cycle, which saw four states pass ballot initiatives legalizing nonmedical marijuana, one in five Americansnow live in a state where it's legal to smoke weed without a doctor's letter.

The industry is on track to post $20.2 billion in sales by 2021.

Here's a summary of where Americans can light up legally so far in 2017.

Arkansas and Florida start moving toward voter-approved medical marijuana systems, Massachusetts activists push for greater patient access, and more.

Massachusetts continues the 115-year-old tradition of restricting marijuana sales, despite the passing of a ballot initiative in November. The Massachusetts House and Senate passed a bill Dec. 28 in less than half an hour that will push back the timetable for the opening of retail marijuana stores by six months to July 1, 2018.

Marijuana advocates are trying to block an anti-legalization lawmaker from becoming the state Senate’s point person on pot, contending that his outspoken criticism of recreational marijuana makes him unfit for the position.

The advocates are lobbying Senate leaders not to appoint Senator Jason M. Lewis as the co-chairman of the new Committee on Marijuana because Lewis was a key opponent of Question 4, which legalized pot purchase, possession, and use.

Jim Borghesani, who helped run the ballot campaign and now works for the national Marijuana Policy Project, said advocates don’t think the Legislature should tinker with the law at all before the marijuana oversight body it creates has time to make regulations.

ArcView Market Research released their annual cannabis market summary, and the numbers are staggering for the legal marijuana industry. In their 4th edition of The State of Legal Marijuana Markets they report that an amazing 30% growth rate occurred in the industry, which makes it the fastest growing industry in the country by far. The pace is even greater than the dot-com era, which grew at only a 22% rate.

Certified nurse practitioners would be allowed to authorize medical marijuana use by patients under new rules proposed by Massachusetts health officials.

Public hearings on that and other revisions to the medical marijuana program are scheduled on Tuesday in Boston and on Thursday in Holyoke.

Under current rules, patients need permission from their doctors before they can register to use pot for certain medical condition. Under the proposed new rule, nurse practitioners could provide certification, although a physician must still certify use by any minor.

Another proposed change would allow caregiving institutions to register with the state to administer medical marijuana, rather than forcing each employee to register separately.

A vote over the holidays puts the brakes on recreational pot shops.

It’s been two weeks of ups and downs for those celebrating Massachusetts’ new legal marijuana law. While many were taking their first-ever fully legal puffs inside their living rooms over the holidays, lawmakers gathered almost completely without public scrutiny to slow things down—keeping in place, for a little while longer, a temporary system that allows adults to possess and use marijuana, but not to sell it or to buy it in a store.

Massachusetts governor Charlie Baker [official website] signed Senate Bill No. 2524 (SB 2524) [materials] on Friday, which will delay part of a voter-approved marijuana legalization initiative [text] by six months. Massachusetts citizens voted 53.7% to approve the "possession, use, distribution, and cultivation of marijuana," with the condition that it would be regulated similar to alcohol. The licensing of cannabis shops was set to begin on January 1, 2018, but SB 2524 moves that date to July 1, 2018. The legislature says the delay is necessary to conduct further surveys regarding patterns of use, incidents of impaired driving and hospitalization, and the economic impact of marijuana legalization.

Massachusetts voters passed a ballot initiative to legalize the possession or home-grown marijuana in the last election. However, residents may need to wait longer to buy the legalized weed.

On Wednesday, Massachusetts lawmakers passed a legislation that will postpone the opening date for recreational marijuana for six months. Residents cannot buy legalized weed until July 2017.

According to the Boston Globe, the House and Senate held an informal meeting on Wednesday morning and ruled for the unexpected legislation.

The ballot initiative to sell recreational marijuana in stores was set for January 2017. However, legislators needed more time to finalize the sale regulations for marijuana.

Market and analytics experts published a study predicting one industry to blaze by all others in the Bay State, growing beyond $1 billion annually by 2020:

Marijuana.

With retail sales of the substance beginning in 2018, the study painted a picture of a changing commonwealth -- a destination visit for "canna-tourists" by the thousand -- the marijuana hub of New England, if not "the world."

Marijuana data and investment firms ArcView Market Research and New Frontier published the study earlier in the year, before the Election Day legalization vote.

Troy Dayton, CEO of The Arcview Group, made a bold prediction in a statement on the study.