Legalized recreational marijuana is coming to Maine soon, but it’s highly unlikely it’s coming to the entire state.

The state’s rules are designed to allow municipalities to opt in or out of allowing sales of adult-use marijuana, which voters legalized in 2016, and only a handful of cities and towns have laid the groundwork for retail sales. That means it’s possible marijuana will be for sale in only a few of the state’s nearly 500 cities, towns and plantations when it arrives in stores, likely in 2020.

An exact number of how many communities will opt in is difficult to come by because municipalities are in different stages of deciding whether to grant licenses locally. Some have signaled they want no part of pot. The result could be that large parts of the state, such as rural Aroostook and Washington counties, will have few retailers.

The state hasn’t even finished crafting its rules and regulations, so even municipalities that want pot are in a holding pattern until that’s done. The Maine Legislature could vote this week.

Some communities have done a lot of prep work, so they’ll be ready when it is. Two that are deep into the process are Portland, the state’s largest city, and Hallowell, a liberal enclave in central Maine.

In Portland, spokeswoman Jessica Grondin said the city has done lots of pre-planning work. It’ll likely be one of the first places in the state where marijuana is available for adult use.

But it’s possible parts of the state will be “marijuana deserts,” where the drug is legal but not available, said David Boyer, Maine political director for the pro-legalization Marijuana Policy Project. It’s also possible that problem will fade over time if Maine municipalities see a smooth transition to legal cannabis and decide later to opt in, said Boyer and other marijuana backers.

“It makes sense the state has put it back to local communities because that’s who has to deal with the licensing, the permitting and all of that,” said Cliff Miller, chief executive officer of Atlantic Cannabis Collective in Auburn.

Other states that already legalized pot have also experienced slow adoption of local marijuana sales. Colorado was among first two states to go legal in 2012 and still only about 100 of the state’s 272 municipalities have signed on to allow recreational pot businesses, according to the state’s Marijuana Enforcement Division.

The Maine Municipal Association is working with cities and towns in the state to craft rules that work best for them, said Eric Conrad, spokesman for the association. For many municipalities, that will likely mean no sales at all, at least at first.

“It’s a smaller percentage of our members who are opting in,” Conrad said. “But it might just be like alcohol one day.”

Acceptance of commercial marijuana businesses at the local level often takes time, but more cities and towns tend to catch on after the early adopters are successful, said Jordan Wellington, vice president of government affairs for VS Strategies, a Denver-based firm that focuses on cannabis policy.

“Over time many communities that initially ban retail marijuana establishments change their laws to now accept those businesses in their community,” he said.

In the early days of legalization, buying marijuana in Maine will likely mean long drives for many, said Charles Hawkins, who owns a North Windham medical marijuana dispensary. He said that will likely result in more people seeking a medical use card.

“Nobody wants to drive down 302 from the Lakes Region to Portland, through that traffic in the summer, or down River Road in the winter when it’s icy,” he said. “Nobody wants to do that.”