Trevor Hughes

USA TODAY

DENVER — Marijuana is rapidly becoming a big, semi-legal business across the country, with $5.7 billion in sales last year and tens of thousands of people working and paying taxes as they cultivate, package and sell cannabis.

Colorado, Alaska, Oregon, Washington state and Washington, D.C. have all legalized adult recreational use, and 23 states and the District of Columbia permit some form of medical use. That’s despite the fact that marijuana remains an illegal drug and Schedule 1 controlled substance at the federal level.

Across the country, thousands of people are rushing into the industry, struggling to work within a conflicting patchwork of state laws and local regulations, all the while operating largely without accounts at banks, which are fearful of running afoul of federal drug-trafficking laws.

The industry is only expected to grow in 2016, particularly if California voters this fall decide to legalize recreational use, according to the newly released 4th Edition State of Legal Marijuana Markets Report from from ArcView Market Research and New Frontier, a cannabis-focused data-analysis firm. Much of the increase is attributed to adult use market sales, which hit $1.3 billion last year. By 2020, adult use and medical marijuana sales are expected to reach nearly $23 billion, triple this year.