Say the words “fast food” to many Americans, and they’ll immediately turn up their noses, picturing grease-slicked tables, sullen cashiers and calorie-laden menu options.

But one fast food chain stands apart from the others in terms of customer satisfaction: Chick-fil-A. The chicken restaurant gets the highest customer satisfaction score of any fast-food chain that American Customer Satisfaction Index has measured over its 21-year history, according to a survey of more than 4,700 Americans released Tuesday from the ACSI.

The fast-food chain scores an 87 out of 100 in terms of customer satisfaction, making it not only the highest-scoring fast-food chain this year, but also the highest scoring company out of the more than 300 large companies that ACSI measures. And in a Harris Poll of 97,120 U.S. consumers, Chick-fil-A ranked as the top chicken restaurant in America.

“They do one thing and they do it well — chicken,” says David VanAmburg, managing director of the ACSI, about why the restaurant is so popular with its customers. Or as Wall Street Journal food writer Charles Passy puts it, “The Chick-fil-A chicken sandwich — grilled or fried — is one of those Great American Things.”

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Despite these high scores, Chick-fil-A has angered many consumers with its anti-gay politics (in 2012, the president of the company said he was against gay marriage), and some customers still refuse to go to the restaurant because of this. (MarketWatch’s Moneyologist weighed in on whether you can go to Chick-fil-A if you don’t agree with its politics.)

In response to complaints about its president’s beliefs, the company said the Chick-fil-A brand represents many dimensions of humanity via its 80,000 employees. “But what they all have in common is a heart for service and passion for making great food,” a spokeswoman said.

Others knock the menu and say many options aren’t the healthiest (the Spicy Chicken Deluxe sandwich clocks in at 570 calories and 27 grams of fat — which puts it roughly on par with the McDonald’s MCD, -1.03% Quarter Pounder with Cheese in terms of fat and calories). The Chick-fil-A spokeswoman said the company is “ever-mindful of creating a healthy balance of ‘choice’” for customers, and provided a link to meals it offers that are less than 500 calories.

But despite these criticisms, the chicken chain is flourishing: In 2015, its sales hit $6 billion, marking 48 straight years of sales growth.

Chick-fil-A’s high score comes at a time when customer satisfaction with fast-food restaurants in general is rising (customer satisfaction with fast-food restaurants climbed two points from last year to 79 out of 100). VanAmburg says this is due, in part, to better quality ingredients (for example, many fast-food chains have vowed to use cage-free eggs) and consistently low prices.