In 2015, state legislators considered bills to legalize marijuana in 21 states, decriminalize marijuana possession in 17 states, and legalize medical marijuana in 19 states.

Most of the action in 2015 was aimed at achieving substantial victories in 2016, which is slated to be the most successful year in the history of the movement to end marijuana prohibition.

With this in mind, the Marijuana Policy Project is hereby releasing its top 10 list for 2015. I'm excluding international and scientific developments, instead focusing on policy developments in the United States.

10. Local Decriminalization Measures: In Florida, seven local governments (including Miami-Dade County) opted to allow officers to cite, rather than arrest, adults found in possession of marijuana. And in Michigan, an average of 55% of voters in East Lansing, Portage, and Keego Harbor decriminalized marijuana possession.

9. Everything In Texas: The Texas Legislature and governor's office — all controlled by Republicans — enacted a bill to allow specially licensed businesses to sell low-THC marijuana to patients with intractable epilepsy, thereby setting the stage for a broader medical marijuana bill to pass in 2017, which is now more possible since a principal opponent of medical marijuana in the state House announced her retirement. Just as significantly, the key House committee passed a pair of bills toremove criminal penalties for marijuana possession and to legalize marijuana like jalapeÃ±os; there were enough votes to pass the former bill on the House floor, but the legislature ran out of time.

8. Medical Marijuana Expansion In Four States, D.C., and Puerto Rico: Numerous states expanded their existing medical marijuana laws to cover a larger list of medical conditions. Delaware added certain types of autism; Arizona added post-traumatic stress disorder; Minnesota added intractable pain; and the District of Columbia now allows physicians to recommend cannabis for any condition. In Hawaii, the list of medical conditions remained static, but the legislature and Gov. David Ige (D) enacted legislation to expand the existing grow-your-own law to allow for the sale of medical marijuana by 16 dispensaries. And in Puerto Rico, Gov. Alejandro Garcia Padilla (D) signed an executive order legalizing medical marijuana.

7. Medical Marijuana In Pennsylvania, Nebraska and Utah: The Pennsylvania Senate passed a medical marijuana bill, Republicans in the state House recently removed the obstacles that were preventing the bill's passage, and Gov. Tom Wolf (D) is ready to sign it as soon as the legislature passes a final bill. In Nebraska, the only unicameral legislature in the country passed a medical marijuana bill, which the legislature will need to do two more times before the bill can be sent to the governor. And in Utah, the state Senate defeated a medical marijuana bill by only one vote.

6. Marijuana Decriminalization in Illinois: The Illinois Legislature passed a bill to remove the threat of arrest and jail for marijuana possession, but Gov. Bruce Rauner (R) issued an amendatory veto requesting relatively minor changes, so a compromise bill has been introduced and will almost surely pass in the fifth-most-populous state in early 2016. Also, the state House in New Hampshire and Senate inNew Mexico passed similar decriminalization measures, but the two states' other legislative bodies didn't take action.

5. Decriminalization in Delaware: In Delaware, Gov. Jack Markell (D) signed into law a measure that removed the threat of arrest and jail for marijuana possession, making Delaware the 20th state to decriminalize or legalize marijuana possession. (And while Louisiana didn't decriminalize marijuana, the state governmentsignificantly reduced the penalties for marijuana possession.)

4. Legalization Ballot Initiatives in Five States: Many people were worried that competing legalization initiatives might appear on a few states' ballots in November 2016, but this won't be the case. In Arizona, California, Maine, Massachusetts, andNevada, it's highly likely that there will be only one legalization initiative on each statewide ballot, which means four or five of these states will legalize marijuana on the same day in less than 11 months.

3. U.S. House of Representatives: An amendment by Congressmen Tom McClintock (R-CA) and Jared Polis (D-CO) came within nine votes of temporarily ending marijuana prohibition on the federal level; specifically, their amendmentwould have prevented the U.S. Justice Department (DOJ) from interfering with the legalization laws in Alaska, Colorado, Oregon, and Washington, as well as the medical marijuana laws in 23 states. The U.S. House also inched closer to fixing the banking and tax laws that are plaguing the canna-business industry.

2. U.S. Senate: Bernie Sanders (D-VT) grabbed some headlines when he introduced the first-ever bill to legalize marijuana in the U.S. Senate. Just as significantly, Corey Booker (D-NJ) and Rand Paul (R-KY) introduced in the Senate the first-ever, comprehensive medical marijuana bill, which now has 16 co-sponsors. In the meantime, the Senate Appropriations Committee passed an amendment to prohibit DOJ from spending taxpayer money to interfere with state medical marijuana laws, as well as a second amendment to allow physicians in the U.S. Department of Veterans Affairs to recommend medical marijuana to vets.

1. Presidential Candidates: All three of the major Democratic candidates for president said they support allowing states to regulate marijuana as they see fit. This was impressive, but it was even more impressive when nine of the 17 Republican candidates said the same thing, and even six of the remaining eight "bad" Republicans said something good about medical marijuana or decriminalization.

In 2015, the table was set in other ways that will lead to a healthy serving of marijuana policy reform in 2016. For example, Alaska and Colorado appear poised to allow some form of on-site consumption of marijuana in private establishments (similar to alcohol bars), which would give these two jurisdictions the two best marijuana laws in the world.