If you are of an age — say a baby boomer or thereabouts — you probably remember the summer family vacation.

It probably went something like this: Your parents piled you and your siblings into the back of the Pontiac or the Plymouth or the Chevrolet, or maybe even one of the new Ford station wagons, and set off to see the country.

Maybe you remember squabbling in that back seat because your brother stuck his foot on your side of the car. Maybe you played the license game, trying to be the first to see license plates from all the states. Maybe you wanted to stop at the clean, shiny restrooms that gas stations were touting, where you could also pick up a free map of whatever state you were in. Maybe when you got hungry, you mother pulled out a loaf of bread, some peanut butter and jelly and made you a sandwich.

Maybe you had more adventures than you wanted: a flat tire, a disastrous "shortcut," a radiator that boiled over in the desert heat.

Maybe you remember going to Disneyland, Yellowstone or even the nation's capital. Maybe you got to buy some souvenirs that you treasure to this day.

What you probably didn't realize at the time was that you were part of a trend. You were participating in a "Golden Age of Family Vacations."

That era began as the end of World War II ushered in a time of prosperity.

"Summer vacations became an established summer tradition," says Susan Sessions Rugh, a history professor at Brigham Young University, who has written a cultural history called "Are We There Yet? The Golden Age of American Family Vacations" (University Press of Kansas, $29.95).

The golden age lasted until about the mid-'70s, she says, "when family road trips declined in popularity. Family vacations continued after that, but they weren't the same. The family wasn't the same."

Rugh has always been interested in the history of the family, she says. "As I talked to people about their family life, I realized that one of the things they remembered most was a vacation. I decided that was a fun way to look at the history of the family — through leisure activity."

But what started out as a history of the family "turned into a history of a time, a history of an age, a place. Along the way it also became a history of tourism and travel."

In studying the vacations of that time, she says, "the one thing that surprised me the most was how much trouble it took to take a family vacation. The work, the preparation, the driving, the money spent — the lengths that parents went to in order to take their children places."

So, why did they do it?