The West was won by brush and camera. Or was it camera and brush? To hear the photo historians tell it the early photographic images by T.H. O'Sullivan, Carleton Watkins and William Henry Jackson played the major role in luring 19th-century Americans to the Far West.

But art historians claim that it was the exuberant landscape paintings of Thomas Moran and Albert Bierstadt that spurred them on.

"You can't separate the two," says Smithsonian curator of photography Eugene Ostroff, and he sets out to prove it in a fascinating show which opened yesterday at the Smithsonian's Museum of History and Technology.

Entitled "Western Views and Eastern Visions," the exhibition includes 170 vintage photographic images -- along with a smattering of related paintings, drawings, prints and watercolors -- representing the earliest images created by those who accompanied the first expeditions to the Far West.

After the Loiusiana Purchase in 1803, which extended the western boundary from the Mississippi to the Rockies, many such forays were mounted by the government, the military, the railroads, scientists and an occasional foreign prince. From the start, painters had been there to give eyewitness to the written accounts.

But many citizens and members of Congress remained skeptical of what seemed tall tales, both verbal and visual. Painters, after all, could exaggerate. "Photography remained the missing ingredient," says Ostroff. "When it was introduced in the 1850s, it became a vital element in convincing Congress and the public of the richness of the new land."

Indeed, when congressional funding was needed in 1868 for a second U.S. geological expedition, an exhibition of T.H. O'Sullivan's photographs mounted on Capitol Hill turned the tide. Similarly, the photographs of William Henry Jackson played a major role -- along with paintings by Moran -- in establishing Yellowstone as the first National Park.

It is not hard to imagine the impact these first photographs must have had. Here for the first time was the unarguable, breathtaking truth about the beauty of the Grand Canyon, the cliff dwellings of the Canyon de Chelle, the boundless wonders of what would soon become -- with the help of these images -- Yellowstone and Zion National parks.

Here, too, were scenes of Western life, the Indians, cowboys, the images for which collectors now pay hundreds, sometimes thousands of dollars. There was a time when these photographs by O'Sullivan, Watkins, Jackson and others could be purchased at the Department of the Interior at cost.

Stereographic photographs, taken with a twin-lens camera, also proliferated and wowed millions -- both by their images and by the three-dimensional effect effect they produced in a viewer. Selling photographs for use on stereocards was often the main source of income for these early photographers, who received no salary or expenses for the backbreaking task of hauling their wagons filled with equipment, glass plates, chemicals, food and clothing. Several images portray both the hardships and joys of their pioneering work.

All of the photographers represented in this show, particularly those who worked for the four great governmen-sponsored surveys, were artists as well as superb technicians, and in their romantic moments they exhibit all the awe expressed in the paintings of Bierstadt and Moran.

Paintings and photographs are often juxtaposed here, allowing telling comparisons. In one pair of works portraying the steaming geysers of Yellowstone, for example, a watercolor by John Renshowe wins hands down for the sense of wonder it conveys. The photo is mere artless documentation. Elsewhere, however, a drawing by W. H. Holmes features a woman's profile emerging from the rocks of Pike's Peak and strains credulity. It also suggests why photographs were needed before the whole magnificent truth could be discerned.

This show was organized by Eugene Ostroff for the Smithsonian's Traveling Exhibition Service, and will begin a two-year national tour after closing here in January. A catalogue, sorely needed, will be published at that time.