Short Story/Novella in Which People Living in What they Think is Small Town Fifties America Find Look Magazine and Don't Recognize Anything in It

This is probably from the mid-to-late fifties. It involved families living in what seemed to be normal, small town America of the time. But two boys found in a garbage dump or in a nearby landfill a copy of "LOOK" magazine from their time period (1955? 1957?). Their problem was that they and their families didn't recognize any of the people or events that were reported in the magazine.

The tone of the articles in the magazine matched their actual lives in that the magazine reported world events, trouble spots, celebrities, politics, and had advertisements for cigarettes and TVs, etc. but the facts were completely different. I think the magazine was a magazine from 'real' America and they were living in a 'fake' America, i.e., they had been brought up in a separate isolated environment with everything different but now had found something from the 'real' world. The tone of the story was that they were never supposed to know about any of this. Maybe, just maybe, part of it was a story about Marilyn Monroe but none of the people had ever heard of her. I can't remember much more than that but I have a nagging thought that they were part of some controlled environment experiment by the US Military.

Answer

I think this is the novel Time Out of Joint by Philip K. Dick.

The children find the magazines in some ruins rather than a rubbish dump:

At sunset, Sammy Nielson put in a last tardy hour galloping around the Ruins. Together with Butch Cline and Leo Tarski he had dragged a mass of roofing slats into a heap to form a real swell defensive position.
...
Lying down, he scooped up handfuls of plaster and chickenwire. Bits covered him as he labored. In the half-light, straining to see, he found a soggy yellow blob of paper. A phone book. After that, rain-soaked magazines.

One of the magazines is:

The next magazine had more pictures in it; something like Life. But the paper was not as high-quality as the Luce publications’ paper. Still, it was a first-line magazine. The cover was gone, so he could not tell if it was Look; he guessed that it was Look or one he had seen a couple of times called Ken.

And the magazine has an article on Marilyn Monroe:

The next picture-story—A lovely blond Norse-looking actress. Reaching up, he moved the lamp so that it cast more light on the page.
...
Under the picture was the caption, Marilyn Monroe during her visit to England, in connection with the filming of her picture with Sir Laurence Olivier.
"Have you heard of her?" Margo said.
"No," Ragle said.
"She must be an English starlet," Vic said.
"No," Margo said, "it says she’s on a visit to England. It sounds like an American name."

At the end of the book we discover that:

The town is run by the military. Earth is at war with colonists on the Moon and one of the people in the town, Ragle Gumm, has an ability to see the future and predict where the next attack from the Moon will come.