The year was 2014. The pub was O’Neil’s on Wells in the heart of Chicago’s financial district in the shadow of the Chicago Board of Trade, one of the world’s oldest exchanges for swapping futures and options. Inside the Irish-themed neighborhood hangout, Sonny Meraban noticed activity bubbling up around a well-placed Bitcoin ATM. A man happened to be standing near the machine so Meraban started talking to him. The man turned out to be the owner/operator of the entire company.

“I couldn’t believe the margins,” recalls Meraban, who was already familiar with the digital currency, having an account at San Francisco-based Coinbase, a platform for buying and selling cryptocurrencies. Meraban, a longtime real estate investor, was looking for an alternative investment. He bought his first Bitcoin ATM for $7,000 and installed it at a Chicago liquor store, allowing users to buy bitcoin.

“The first one did $30,000 in sales in 30 days,” Meraban says. “That’s when we realized that Bitcoin is being bought by people that are underbanked and have a need to make payment transfers such as bill payment.”

Suddenly, a new trend was developing and it became a common assessment from Bitcoin ATM operators from Boston to Los Angeles. The Federal Deposit Insurance Corp. estimates that 25% of U.S. households are unbanked or underbanked — lacking a bank account outright or forced to use alternative financial services such as payday loans, money orders and check cashers.

Bitcoin ATMs, exchanges and other trading platforms are helping this underserved segment conduct financial transactions. Even Microsoft, Expedia and Newegg are accepting bitcoin as currency. Cash App, the mobile payment service developed by Square Inc., announced in June that it would allow users to deposit bitcoins into their accounts.

When Meraban purchased his first bitcoin ATM, there were only a few hundred across the globe. Now there’s more than 5,400, according to the latest figures compiled by Statista. The lion’s share resides in the U.S. Meraban’s company, the aptly named Bitcoin of America, has been a top player in domestic expansion, building its ATM count to more than 25 in Chicago and 30 in Detroit. The company expanded into other Midwest cities, before covering East and West Coast markets. The company has 21 machines in California, mostly in the Los Angeles metropolitan area, and has steady growth plans here, given the size of the market—the world’s largest for bitcoin ATMs.

Bitcoin of America ATMs are primarily installed in liquor shops, gas stations, convenience stores, vaping retailers and other locations with heavy foot traffic. Store owners receive a monthly rent to house the machines. Bitcoin of America, which is registered with the U.S. Department of Treasury, has amassed nearly 200,000 customers since its inception. Meraban takes pride in his compliance program and is fully BSA/AML compliant. “We have one of the strongest compliance programs, if not the strongest.”

A move into Las Vegas brought five more machines, and a new device for transactions: the tablet, which carries the same business model, with a twist. Under the tablet model, a store operator receives $2.50 per transaction, with escalating bonuses based on volume. The tablet allows customers to have a more personalized experience as they’re assisted through the purchase by a store teller who collects their cash on behalf of Bitcoin of America.

Meraban’s goal is to cover the market with a more hands-on approach as he believes the tablets will allow users to buy Bitcoin in a safer, easier, and more convenient method. Customers can also buy Bitcoin online with a wire purchase through Bitcoin of America’s website. This exchange platform allows users to purchase larger amounts of cryptocurrency for a smaller fee than at a Bitcoin ATM or tablet location.

Unlike other digital currency ATM operators, Bitcoin of America only sells Bitcoin and Litecoin (i.e. another major cryptocurrency). At one point the company processed five cryptocurrencies, but narrowed down its offerings.

“The sales just aren’t there for other cryptocurrencies,” says Meraban, who has spent more than $1 million in compliance costs.

Bitcoin is one of the most volatile traded assets anywhere. Late last month, the currency lost $20 billion in a one day sell-off, erasing much of its 200% gains for the year. The decentralized cryptocurrency crossed the $10,000 milestone in late June, hitting a 52-week high of $13,826.76 on June 26. Since then, it’s nosedived 42%, recently trading at about $8,050, with a market cap of $145 billion.