The restaurant is more than just a place to eat for Pullman residents and Washington State University alumni alike.
In 1973, a drive-in restaurant opened on Pullman's Grand Avenue.
"When you come to Pullman, and you say, 'Well what's the one thing that I can get in Pullman that I really can't get anywhere else?' and that's Cougar Country," said Cougar Country Assistant Manager Brian Power.
Decades later, Cougar Country is still a favorite of Pullman natives and Washington State University Cougs.
"It's like our hometown restaurant," said customer Annalisa Kunkel. "It's the Pullman restaurant."
"We are a landmark," said Cougar Country General Manager Jodi Meyer. "People know we're here and especially alumni. Every time they come back they have to stop by here, which I hear that all the time."
Cougar Country has been the burger joint in Pullman for forty years, but what they're best known for is this fry sauce.
"The people seem to absolutely love our fry sauce, and we'll have people come in and just get the fry sauce," said Power. "They'll like buy the fry sauce by itself."
"You ask any WSU student, any returning alumni, when they come back to Cougar Country, they want their fry sauce," said Meyer.
They'll admit that the sauce is just ketchup and mayonnaise.
"With extra love, ya," said Power.
But that doesn't mean it's easy to make at home.
"I have told people exactly what is in it," said Meyer. "I have shown them our ingredients, what we put into it, and they say they can't replicate it."
Or take home for that matter.
"One person got like ten different of those fry sauce cups, and then they tried to take them home, because everybody loves the fry sauce here," said Kunkel.
Whether it's the sauce or the smiles, the people who work there can see Cougar Country staying open for at least another 40 years.
"You can never get enough Cougar Country," said Meyer.
In celebration of their 40th year in Pullman, Cougar Country is giving all of their customers 40% off their order all day Tuesday.