Weed legalization advocates are running out of friendly territory.

The movement has swept the country over the last decade: Nearly half of Americans now live in a state where anyone at least 21 years old can legally possess and purchase marijuana.

Legal weed sales are slated to top $35 billion this year — and are expected to surpass $70 billion by 2030, according to New Frontier Data.

Since December, five new recreational markets have launched, including New York, Missouri and Maryland, where sales began on Saturday. Those states alone added 37 million people to the legal weed column.

But that’s left plenty of holdouts — overwhelmingly in more conservative territory, particularly in the deep South. And there are increasing signs of a legalization backlash in deep red America: Voters in four states — Arkansas, Oklahoma, North Dakota and South Dakota — have rejected adult-use referendums in the last nine months. Every county in Oklahoma voted against a March referendum that would have legalized possession and sales for adults.

“The lower hanging fruit are increasingly picked,” said Karen O’Keefe, director of state policies at legalization advocacy group Marijuana Policy Project. “It’s going to require moving into states that are in many respects more challenging.” [Read more at Politico]