For a kid growing up in the post-World War II suburbs, it was a comforting world of Captain Kangaroo on the tube, a new washing machine in the basement, a shiny gas guzzler in the carport and a bomb shelter in the back yard.

"This is our childhood," said Roger G. Kennedy, director of the National Museum of American History, where he introduced a new exhibition that takes a nostalgic look at the lives of children born during the Cold War years.Kennedy meant not only the childhood of the current baby boom generation of parents but, in a deeper sense, the innocence of a nation that yearned only for peace and the emblems of middle-class prosperity.

The show, titled "This is Your Childhood Charlie Brown: Children and American Culture, 1945-1968," opened Wednesday at the Smithsonian Institution museum for a six-month engagement through next April.

It contains more than 500 artifacts and graphics from an America that would soon lose its innocence in Vietnam and the social upheavals of the late 1960s.

Among them is Charles M. Schulz's first "Peanuts" comic strip, which appeared Oct. 2, 1950. Perhaps more than any other cartoon characters of that era, Charlie Brown and his friends mirrored the hopes and fears of postwar America with a gentle, captivating humor.

In an age when children were taught to live by society's rules and obey their parents, their TV heroes frequently wore uniforms. Even Bob Keeshan's Captain Kangaroo wore a uniform jacket with a badge as a "figure of benevolent authority."

It was the world according to Dr. Spock, whose lab coat and spectacles are on display along with the drafting table where he wrote his best-selling paperback, "Baby and Child Care," for a generation of worried mothers. Parents worried, too, about communism and nuclear attack. Their children's toys included a Gilbert U-238 atomic lab and Civil Defense medical kit among the hula hoops, Barbie dolls, GI Joes, Lassie lunch boxes and Davy Crockett coonskin caps.

Also on display are such postwar images as a model of the Sputnik satellite, a space helmet, Dale Evans and Nurse Nancy books, a pink chenille bedspread, a Captain Video game, an Annie Oakley cowgirl outfit, a "Ding Dong School" record player and "Romper Room" diploma and an Easy-Bake toy oven.

Curator Charles McGovern, a historian of popular culture, said the exhibition seeks to highlight some of the myths and realities of what is remembered today as "a very calm era."

Actually, he said, "happy suburbanites and the threat of nuclear war lived side by side" along with growing urban poverty and racial divisions that erupted into social conflicts in the 1960s.

Kennedy said "the whole fabric of American society began a long unraveling."