Kristi Kelly didn’t realize how good she had it. For two years after opening a medical marijuana dispensary in 2009, she was able to bank like any small business owner—accepting credit cards, depositing cash, and writing checks. In 2011 the U.S. Department of Justice issued a memo reiterating that federal law prohibits helping businesses that sell marijuana, even if they are legal under state law. That made banks nervous, and one by one they closed Kelly’s accounts. While Colorado has legalized the sale of marijuana for recreational use, Kelly is still trapped in an all-cash economy, forced to develop elaborate systems to operate efficiently yet safely.