Let's head on down to the Library ofCongress and punch up Montana Slim's "There's a Love Knot in My Lariat" on the free jukebox. Afterward we can look at the "Roy Rogers Official Flash-Draw Holster Outfit" you got for Christmas in the '50s. At the Library of Congress? Yep. A roundup of cowboys, real ones and mythical pop heroes, is turning two floors of the Madison Building, the Library's new section, into the OK Corral beginning this Saturday. The maverick exhibit lassos a sacred national myth, from the 1880s' open-range ranchers -- "young, heroic, independent and relentlessly Anglo-Saxon" -- to the 1980s' cowpokes armed with the latest in electric cattle prods. From tumblin' tumbleweeds to the seductiveness of the Marlboro Man, in "The American Cowboy" we're at home with a range of cowboy images: the rugged outdoorsman in wide-open spaces, the rodeo daredevil, the crooner in a fringed shirt, the strong silent type on film, the pitchman for everything from Cream of Wheat to hot tubs and the modern rancher all ride tall in photos, paintings, artifacts, film clips, recordings, books, posters, broadsides and whatnot -- 370 items in all. Fables of rowdy, pistol-totin' buckaroos are documented since Buffalo Bill and the boys. Barroom brawls were first depicted on stage, then in dime novels and magazines like the National Police Gazette. Next, Frederic Remington romanticized the image, illustrating lonely types in cow country and casting the "Bronco Buster" in bronze. (The show's catalogue reveals Remington as a racist who, fearing that the Northeast was being lost to the immigrants, looked westward for ethnic purity.) The romantic trend took hold: Owen Wister's "The Virginian" stood even taller in the saddle than John Wayne (who gets his licks in, too), spurring the cowboy craze back East. A 1902 first edition of the book is displayed beside lithographs illustrating the play "The Great Train Robbery." A shelf- full of Clarence E. Mulford's Hopalong Cassidy series complements stereographs of Theodore Roosevelt in Rough Rider attire. Tom Mix, star of western B movies; Will Rogers, cowboy-philosopher; William S. Hart, silent-screen favorite; and novelist Zane Grey are all shown to have galloped across the national psyche. But it wasn't all glamorous showdowns. "A Cowboy's Life Is a Dreary Life," warbles a cowpuncher from 1942 in another of the show's musical installations. Historians are still debating whether cowboys sang to the herd. Why not? It was a long time between square dances. Another cowhand describes a six-month trail drive as "an endless grind of worry and anxiety, which only a strong physical frame could stand." Only a few cowgirls show up, branding calves or performing rodeo tricks. Mainly, it was a man's world and a dog's life. As the macho horsemen must have asked, why can't a woman be more like a cow? THE AMERICAN COWBOY -- Saturday through October 2 at the Library of Congress, James Madison Memorial Building, 101 Independence Avenue SE.