By the time the new millennium arrives six months from now, countless words and pictures will have been deployed in mostly failed attempts to summarize the remarkable American century just past. Some will have a long shelf life. Most will not. But no museum show is likely to come along that will take a more encompassing, open-minded look at 20th-century American art and culture than the extravaganza now at the Whitney Museum of American Art here.

A monumental undertaking, "The American Century: Art & Culture, 1900-2000" is really two successive shows, each covering a half century and filling the entire museum. The first installment of 600 objects dating from 1900 to 1950--paintings, photographs, film clips, architectural drawings, decorative objects and even a streamlined meat slicer--is on view through Aug. 22. Part 2, covering 1950 to 1999, will open Sept. 26 and close next February.

What makes this exhibition unusual, at least in a trendy New York art museum, is that it's about American history, not art history. But artists of every stripe have been marshaled to tell the tale, from George Bellows and Grant Wood to Alfred Stieglitz, Paul Strand, Busby Berkeley, Orson Welles and Irving Berlin.

The names aren't new, but the combinations are, and they spark this show. People with even a modicum of interest in American art, history or cultural history--or life experience in the United States--are bound to find some new fascination here, or at least gain new perspective, if they take time to ferret it out.

Whitney curator Barbara Haskell spent four years tracking down art that grappled with the look and feel of the times in which it was created. Some artists glorified what they saw; others saw trouble beneath the surface. Some unforgettably documented the harsh realities of the Great Depression. Later, still others--like Norman Rockwell--created stirring emblems of the ideals for which Americans were dying in World War II.

Inevitably, Haskell also sought out the American photographers, filmmakers, writers, composers, dancers, architects and designers whose work similarly engaged or reflected contemporary life. (Many viewers, indeed, may come away from this show convinced that of all early-20th-century American artists, the photographers and filmmakers were the greatest.)

Their collective reflections are as varied as the artists themselves. Stieglitz looked at New York and created romantic photographic paeans to its skyscrapers, while Edward Hopper saw human isolation in their shadows. Charles Sheeler glorified the machine age in paintings and photographs, while, in "Modern Times," Charlie Chaplin saw man as its hapless victim.

It is these dynamic opposing perceptions of good and ill, of boundless possibilities and dead-end hopelessness, that tie this tale together. With only a minimal text, viewers are left to reshuffle their thoughts and come to their own conclusions about them. It is these connections--all of which take place in the viewer's mind--that give this show its power.

The result is an avalanche of still and moving images that starts on the fifth floor and cascades down chronologically, more or less a decade at a time, from the last gasp of the Victorian era through early modernism to the jazz age of the '20s, the Great Depression of the '30s and beyond. The exhibition ends where the next installment begins: in the aftermath of World War II.

Within this sometimes-elusive time line, however, Haskell has sensibly divided her show into smaller, more digestible segments focused on particular subjects, such as "The City," "Immigration and New Populations," "Social Reform," "Idealized America" and "Industry as Menace."

From the moment you step off the elevator on the fifth floor, paintings begin to relate to each other in an almost cinematic way. The first thing you see is Cecilia Beaux's belle epoque portrait of "Mrs. Larz Anderson" (1900) with the family emeralds dangling from her cantilevered decolletage. You can almost hear the years zoom by as your eyes pan over to Robert Henri's 1916 portrait of Gertrude Vanderbilt Whitney, the museum's artist-founder, wearing green and blue silk lounging pajamas and a level, self-confident gaze. This is a real woman, not a decorative object.

America's romance with technology and the modern age is expressed in several wonderful paintings and photographs of New York, taken when the city first sprouted skyscrapers and its bustling harbor filled up with steam-spewing ferries and tugs. Jonas Lie's shimmering harbor scene "Path of Gold" is one of the greatest paintings of this genre.

But, captivated by the excitement of this new urban subject matter, photographers especially used the city to express an exuberant optimism about the future of America. Today these urban scenes by Strand, Stieglitz, Alvin Langdon Coburn, Karl Struss, Edward Steichen and others are among the most memorable photographs of the century. However, the only real revelation in this section, titled "Modernity and Urban America," is the rarely seen nine-minute black-and-white silent film titled "Manhattan," made in 1921 by Strand and Charles Sheeler. A passionate, awestruck homage to the power of the city, it is also a tribute to the considerable cinematic skills of Strand and Sheeler, who are best known, respectively, for their photographs and paintings.

Romance quickly gives way to realism in a nearby gallery--one of the most poignant in the show--in which contemporary photographs show a world very different from that inhabited by Whitney and her fashionable friends. While the so-called "Ashcan" painters, whose works hang nearby, saw poverty in Manhattan's streets, they also saw a gritty vitality that makes their paintings seem downright nostalgic when compared with the photographs of Jacob Riis, Lewis W. Hine and Jessie Tarbox Beals.

With the hope of bringing about social reform, these photographers created unforgettable images of exploited working children, the squalor of immigrant life in the Lower East Side tenements and the exploitation of destitute young women forced into prostitution. These subjects were also tackled by painters and sculptors, as we see here. But it's the photographs that we can't forget: Hine's "Making Human Junk," a 1915 poster for the National Child Labor Committee; Beals's "Destitute Mother With Twins"; the women of the New Orleans red-light district by E.J. Bellocq. Forced prostitution is also the subject of a 1 1/2-minute excerpt from George Loane Tucker's "Traffic in Souls," another of the three dozen rare film clips sprinkled through the show, including some by Thomas Edison.

All this, and I still hadn't left the fifth floor! Fortunately, the Whitney has a fine little restaurant, so there's a place for day-trippers to renew themselves. To do the show justice, you should plan to spend the day.

Immigration, technology, mass media, entertainment--all powerful forces of change--are addressed in special sections. "Precisionism and the Machine Age" brings us a cubist cocktail shaker and a skyscraper bookcase. Skyscrapers run like a leitmotif through this New York-centric show, but turn ominous in Hugh Ferriss's utopian "Study for Maximum Mass Permitted by the 1916 New York Zoning Law"--looming hulks of buildings that could have been built, but fortunately weren't.

There are intriguing byways, including a section on the exoticism that followed the discovery of King Tut's tomb in 1922, inspiring some great old Gloria Swanson movies as well as the Egyptian-looking facades of proliferating movie palaces.

Movies pervade this exhibition as they have the century. About 200 films from the period are being shown chronologically throughout the run of the show. They are free with the $12.50 price of admission.

The exhibition itself might also be seen as something of an artifact, reflecting the ways museums have evolved over the years from passive treasure houses into educational institutions and interpreters of cultural history. This multimedia mega-exhibition and its Internet site, www.echonyc.com/ whitney, both sponsored by Intel, may even turn up in the history books as millennial landmarks.

We should remind ourselves that most of the paintings and prints here were ignored by American collectors until recent decades. Except, of course, at the Whitney, which was founded in 1930 and has been the principal advocate of American art ever since. Its reward is in the peerless collection it acquired over the years, both by purchase and by gifts from grateful artists. For this millennial bash, it has been supplemented by loans from other collections.

'THE AMERICAN CENTURY'

The first part of "The American Century: Art & Culture 1900-2000," covering the years 1900 to 1950, will continue at the Whitney Museum of American Art in New York through Aug. 22. Part 2 (1950-1999) will be on view Sept. 26 to Feb. 13.

An illustrated companion book by curator Barbara Haskell (Norton, 408 pages, $60) has been published for Part 1; another will follow for the second. Tickets are $12.50 for adults and $10.50 for seniors, students and people in groups of 15 or more. The public can purchase timed tickets in advance ($2 service charge) by calling 1-877-WHITNEY or by ordering online at www.whitney.org. The museum is open Tuesday, Wednesday, Friday, Saturday and Sunday from 11 a.m. to 6 p.m. and Thursday from 1 to 8 p.m.; closed Monday. The Whitney is at 945 Madison Ave. in Manhattan.

"The American Century" is also accessible through the Whitney's Web site.

CAPTION: Edward Hopper's 1927 "Chop Suey": Depicting the human isolation found in the shadows of a bustling city.

CAPTION: An American collage: Robert Henri's 1916 "Gertrude Vanderbilt Whitney," left, and a scene from the 1936 Charlie Chaplin film "Modern Times." Inset, Weegee's 1945 book of photographs.

CAPTION: Grant Wood's 1930 "American Gothic," one of the 600 objects now on display at the Whitney that spotlight the century's first 50 years.