Every summer, the same scene repeats itself across the United States. The trunk is packed, the cooler is full, and somebody in the back seat is already asking, “Are we there yet?” The great American road trip has begun. For millions of families, this is more than a way to travel. It is a tradition — and maybe the purest expression of a very American idea: freedom.

The tradition even has an address. In 1926, the United States opened Route 66, a highway that ran more than 2,400 miles from Chicago to Santa Monica, California. Newspapers called it “the Main Street of America.” After World War II, cars finally became affordable for ordinary families, and the golden age of the road trip began. Families would drive for days with nothing but a paper map and a full tank of gas. Gas used to cost about thirty cents a gallon, so the biggest expense was usually the ice cream. Route 66 used to be the most famous road in America, and the small towns along it grew rich feeding, fueling, and entertaining tired travelers.

A whole culture grew up beside the highway. Drivers would stop at a diner for pancakes and endless coffee, fill up at a gas station shaped like a giant teepee, and spend the night at a motel, where you park your car right outside your room. Businesses competed to make drivers pull over — which explains one of America’s strangest inventions: the roadside attraction. Texas has Cadillac Ranch, a row of ten Cadillacs buried nose-down in the dirt. Kansas proudly displays the world’s largest ball of twine. None of it is useful. All of it is unforgettable.

Route 66 was eventually replaced by faster interstate highways, and the paper map was replaced by GPS. But the road trip itself never died. Today’s travelers simply have new favorites. They follow a scenic route like California’s Pacific Coast Highway, where the ocean fills the passenger window for hours. They take a detour to see a famous landmark like the Grand Canyon. They stretch their legs at a rest stop, buy snacks in a small town, and photograph absolutely everything.

Why has the tradition survived? Partly because the country is enormous — driving from New York to Los Angeles is roughly the same distance as driving from Lisbon to Moscow. A plane crosses that distance in six hours, but through a little window you see nothing. A road trip turns the same distance into an adventure: strange snacks, small talk with strangers, arguments about the radio, and the feeling that anything could be around the next curve. So when summer comes, Americans still hit the road. As they like to say: it’s not about the destination. It’s about the journey.