Dick's Drive In in Spokane, Washington. This is NOT affilitated with the Dick's in Seattle. In fact it's original name was Panda but its history is quite a story.
In the late '50's its owner tried to bring a McDonald's franchise to Spokane and for one reason or another was turned down. His reaction was to travel to southern California and take a job working in a McDonald's there. A month or so later he returned to Spokane and opened his own drive in serving MCDONALD'S ORIGINAL FOOD. This means french fries stored in a dark room for two weeks, cut with the skin left on, blanched and then fried in 70% animal fat. The exact formula that Mcdonald's followed from the early 50's in Des Plaines, IL (I do not know about San Bernadino) and abandoned by them in 1967. (For anyone that remembers this there was a national advertising campaign announcing their "new" and improved french fries that resulted in a minor outcry among the legions of us who loved the old fries.)
Additionally this drive in, highlighted by USA Today several years ago as the number three highest grossing indiependent fast food restaurant in America, also has the same Speedy Service milkshakes although I believe the hamburgers are slightly different.
Anyway, if you're near Spokane it's right off the interstate through downtown. For those who have forgotten just how good McDonald's original fries were, well, after 34 years they are a revelation. Still the best in America.
By the way two blocks away is a contemporary McDonald's. On a recent Friday afternoon at 12:30 there were approximately 80 people in front of the walk up windows at Dick's along with over 60 cars in their parking lot. Mcdonald's? I counted five in the store with three cars in their parking lot.