– After making hundreds of billions of dollars running casinos, American Indian tribes are getting a good whiff of another potential moneymaker: marijuana.

The first Tribal Marijuana Conference is set for Friday on the Tulalip Indian Reservation in Washington state as Indian Country gets ready to capitalize on the growing industry.

Organizers said representatives from more than 50 tribes in at least 20 states have registered, with total attendance expected to surpass 300.

The gathering comes after the Obama administration announced late last year that it would not interfere with any federally recognized tribes that want to grow and sell pot on reservation lands — as long as they do a good job of policing the industry.

The tribes would join the District of Columbia and four states — Washington, Colorado, Oregon and Alaska — where voters already have approved recreational pot use.

Robert Odawi Porter, one of the conference organizers and former president of the Seneca Nation of Indians in New York, said tribes have “a tremendous economic diversification opportunity to consider” with marijuana commerce.

While it’s unknown how many tribes will seek to take advantage of the change, one analyst warned that any tribe expecting to hit the jackpot might be in for a surprise.

“People keep forgetting it’s a competitive market,” said Mark Kleiman, a professor of public policy at the University of California, Los Angeles, who served as Washington state’s top pot consultant. “And it’s cheap to grow.”

In Washington state, where retail pot stores opened in July, Kleiman said pot growers who sold their product for $21 a gram only a few months ago are now getting $4 a gram.

In January, Minnesota’s Red Lake Band of Chippewa announced that it would study the idea of legalizing medical marijuana and industrial hemp on its reservation north of Bemidji.