Cash is still king in Philadelphia.

The city's mayor signed a new bill on Thursday banning cashless stores starting on July 1, making Philadelphia the first U.S. city to enact such a law. San Francisco, New York City, Washington, D.C., and the state of New Jersey are also weighing similar bills to ban cashless stores. In Philadelphia, the salad chain Sweetgreen is among the many restaurants and coffee shops that do not accept cash. Failing to comply with the new ordinance could result in fines of up to $2,000, The Wall Street Journal reports.

The growing popularity of cashless businesses in the U.S. has ignited a fierce debate about whether these stores discriminate against low-income patrons. Business owners who have gone cashless say that removing legal tender from their stores increases their employees' safety, reduces theft, and also allows stores to be more efficient, as cashiers don't have to handle bills and make change. Critics of the cashless model say these stores end up disproportionally affecting minorities from low-income households who don't have debit or credit cards. 

"It just seemed to me unfair that I could walk into a coffee shop right across from City Hall, and I had a credit card and could get a cup of coffee. And the person behind me, who had United States currency, could not," Philadelphia city councilman Bill Greenlee, a co-sponsor of the bill, told The New York Times. In the U.S., only the state of Massachusetts requires retailers to accept cash, thanks to a bill from 1978.

Philadelphia's legislation includes exceptions for parking garages, rental-car businesses, hotels, and businesses that have a membership model, such as Costco, according to the WSJ report. Last month, Amazon--which plans to open at least 3,000 cashierless Amazon Go stores in the U.S. by 2021--reportedly warned city officials that banning cashless stores would deter the company from opening any brick-and-mortar stores there.