In their heyday, drive-in movie theaters were a dime a dozen, with more than 4000 of them scattered across the U.S. alone. They were so numerous that theaters had to invent gimmicks to outdo the competition—their tricks included “laundry while you wait” and even fly-in movies that could accommodate small planes.

But though it seems quaint now, the drive-in wasn't originally invented as a gimmick. Creator Richard Hollingshead was inspired to create the unique movie set-up because his mother, a larger woman, found it difficult and uncomfortable to sit in regular movie theater seats. Wouldn’t it be great, she mused, if you could just watch films from your car?

He took her seriously, and in 1928 began toying with the idea. Hollingshead started by hanging a sheet from some trees in his backyard and mounting a movie projector onto the hood of his car. He experimented with different conditions, rolling the windows down at various heights to test sound quality, and using a lawn sprinkler to simulate rain. He even built small ramps for his test cars to ensure that rows in the back could see the screen just as well as the rows in the front.

After five years of test-drives, so to speak, Hollingshead received a patent for the “Automobile Movie Theater” in 1933. He spent $30,000 to open the first one—located in Camden, New Jersey—on June 6, 1933. “The whole family is welcome, regardless of how noisy the children are,” he advertised. More than 600 people showed up, paying 25 cents each to watch a 1932 movie called Wives Beware.

Loews licensed the drive-in theater idea from him, which should have made Hollingshead a very wealthy man. Unfortunately, he had trouble collecting, and in 1950, his patent was declared invalid. "He didn't make much money off it,'' his wife, Pauline, later said.

As of 2014, the number of drive-ins in the U.S. had dwindled to just 338.