The all-cash nature of the business has also created huge security concerns for business owners. Many have installed panic buttons for workers in the event of a robbery and have set up a constellation of security cameras at their facilities beyond what is required, as well as floor sensors to detect break-ins. In Colorado, Blue Line Protection Group was formed a few months ago, specializing in protecting dispensaries and facilities that grow marijuana, and in providing transportation security. The firm largely uses military veterans who have Special Operations experience.

Marijuana business owners have devised strategies to avoid the suspicions of bankers. A number of legal operations have opened accounts by establishing holding companies with names that obscure the nature of their business. Some owners simply use personal bank accounts. Others have relied on local bank managers willing to take chances and bring them on as clients, or even offer tips on how to choose nondescript company names.

But the financial institutions eventually shut down many of these accounts after managers conclude the businesses are too much of a risk. It is not unusual for a legitimate marijuana business to go through a half-dozen bank accounts in a few years. While they are active, however, these accounts may have informal restrictions placed on them — some self-imposed — so they do not draw the scrutiny of bankers who may file suspicious-activity reports or would be required to report deposits over $10,000 in cash. The account holders may make only small deposits, and only at night and at certain branches. Mr. Kunkel of Seattle has such an account.

At the largest credit union in Washington State, BECU, about 20 accounts have been shut down in the last three years after it was discovered they were for businesses in the legal marijuana trade, Todd Pietzsch, a spokesman for the credit union, said.

Kristi Kelly, 36, who owns two dispensaries and several marijuana growing operations in the Denver area, said six bank accounts of hers had been canceled in the last 18 months. “Opening the account is not necessarily the problem,” she said. “Our cash deposit levels flag a bank’s compliance division.”

Ms. Kelly, who had just paid $10,000 in cash to the City of Denver for licensing and application fees to expand her business, said that several times a week she carried around tens of thousands of dollars in a bag. “I never felt as illegitimate as the day I had to buy a cash counter,” she said, adding that she spends three hours or so a day just managing the cash from her business’s multiple locations.

A.T.M.s are common in marijuana outlets, but the business owners often have to use their own cash in the machines in case law enforcement authorities conduct a raid and seize the money.