Not an intellectual? Joseph Cornell claimed he was "down-to-earth," he never formally studied art and hated the "gallery trotters" who gave his works highfalutin interpretations. But the National Museum of American Art calls his bluff by divulging his sources.

"Joseph Cornell: An Exploration of Sources" opens Friday in an intimate installation, tracing his famous boxes to a raft of heavyweight source material -- books, magazines, pictures, maps, optical toys, assemblages, recordings, handbills. The man took culture apart and put it back together poetically, elevating free association to an art form.

Cornell was a compulsive collector long before he understood himself to be an artist. He studied the personalities and artifacts of pop and high-brow culture in the 1920s and translated his research into art in the '30s. As a boy, he panicked about the vastness of space after studying astronomy. As an artist, he repeatedly dropped celestial hints such as star maps in his works. One box, "Toward the Blue Peninsula," inspired by an Emily Dickenson poem, shows cagelike wires cut to reveal a window that opens onto endless blue sky. There's freedom or fulfillment or love out there. Another of his masterworks, an untitled penny arcade portrait of Lauren Bacall from 1945-46, comprises photos of the screen idol as a girl and as a starlet and cutouts of New York's skyline inside a blue- stained arcade, tinted the color of early films. (Bacall didn't know anything about the box tribute until the show's curator called to ask about it.)

The exhibit is divided into eight sections: literature (his sources included a French 18th-century story, Dickinson, Mallarm,e, Victorian albums of cut-and-pasted pictures); art (his debts to Juan Gris and Max Ernst); science (the old-fashioned kind -- he was a pack rat for owl pictures); film (his stereoscope and optical toys, Marilyn Monroe ephemera and "hack montage" for the Hollywood studios); theater (playbills, magazines, ticket stubs); dance (ballet scrapbooks); music (sheet music, records, Mozart); and history (from his armchair travels through a Baedeker's guide and photos).

In the '30s, critics irked Cornell by calling his works "toys for adults." They were right. The description still holds "as long as you understand the tradition," says curator Lynda Roscoe Hartigan, who's studied Cornell fulltime since 1976. "It's not a trifle, but we all play with the associations his works evoke for us."

One unavoidable association is to New York: From Coney Island's penny arcades to post cards of Times Square, Cornell's materials were what he called the "flotsam and jetsam of the pavements." From his home in Flushing, he brought New York to life and put a lid on it. JOSEPH CORNELL: AN EXPLORATION OF SOURCES -- At the National Museum of American Art, opening Friday, continuing through Feb. 27. FILMS -- At NMAA, selections from Cornell's collection of early classics, Saturday at 11 and 2.