More than a quarter of those surveyed said they feel comfortable using their credit cards for supermarket purchases, she said.
Retail grocers, long skittish about accepting credit cards, are now seeing the largest increase in credit card use of any retail segment in the state, said Tom Saquella, president of the Maryland Retailers Association in Annapolis, Md.
Area grocers who take them say use of both credit cards and debit cards has gone up.
Those who don't take them say they're going to have to start or risk losing customers.
Part of the reason retail grocers were reluctant to take credit cards was because of the difference in going after someone delinquent on necessities as opposed to luxuries, Saquella said.
"About five years ago, you couldn't find a major supermarket chain in the state that would take them. Now they all take them," he said.
Payment in plastic is getting more common than cash and checks at Martin's Food Market in Charles Town, W.Va., said store manager Joe Reed.
Debit cards account for the bulk of the purchases, Reed said. But credit card use has risen as well.
Younger shoppers seem to use plastic more than older shoppers, he said.
And they're not just putting big purchases on their credit cards, Reed said.
"Sometimes, even under $5," he said.
More people are using both credit cards and debit cards at the Food Lion store on East Wilson Boulevard in Hagerstown, said manager Debbie Toms.
It's better than having them write checks, which take more time to process and can bounce, Toms said.
"It's more convenient. The customer does everything, punches all the buttons. It's even faster than cash," she said.
With all of the big grocery stores taking credit and debit cards, Boonsboro Produce Market owner Joe Reese said he has no choice but to invest in the expensive equipment he needs to take them.
"We're going to have to," Reese said. "People want to pay with both debit cards and credit cards. We have people put stuff back when they find out we don't take them."
County Market in Chambersburg, Pa., used to take credit cards at one register but stopped, said grocery manager Edgar Overcash, who said customer demand has prompted the store to bring back the option.
"A lot of customers come in and ask us if we take charge cards," said Overcash, who said he has had people leave the store when they find out they can't charge their purchases.
The store is in the process of getting new equipment installed so it can start taking them again, he said.
If consumer demand drives which businesses will start taking credit cards in the future, more nontraditional places may be asking "cash or charge?"
Judging by an 81 percent response on the American Express survey, most Americans want merchants in every industry to offer as many payment options as possible, Brookover said.
Consumers cite convenience as their top reason for using credit cards, she said.
They like to be able to track all of their expenses without having to keep a bunch of receipts, Brookover said.
Having an interest-free grace period from the time they charge something until their bill is due helps a lot of people budget their expenses, she said.
Of the consumers surveyed, 70 percent said they routinely pay off their bills each month.