Walt Whitman -- a poet for America; Walt Whitman: A Life, by Justin Kaplan. New York: Simon & Schuster. $15.

Up until the mid-19th century American literature was little more than a weak imitation of that produced in Europe. Noted scholars lamenting this fact called for a native literature that would truly reflect the vitality and freshness of the new land, a cry that culminated in Ralph Waldo Emerson's "American Scholar" address at Harvard in 1837. "Our day of independence, our long apprenticeship to the learning of other lands, draws to a close," he declared. "We have listened too long to the courtly muses of Europe."

Although most of the country, noted scholars included, did not recognize it, this call was soon answered by Walt Whitman. By 1855, when he self-published a thin book of poems bound in green cloth called "Leaves of Grass," America had indeed produced a poet totally its own. Among the freewheeling verses, as vigorous and pioneering as the country in which they were written, the "courtly muses of Europe" were nowhere to be heard.In this biography Justin Kaplan gives us a full-blooded portrait of Whitman and the social milieu that both spawned him and spurned him.

Like Abraham Lincoln, whom Whitman revered and eloquently eulogized in several poems, he was of humble origin, largely self-taught and self-made. Born on Long Island in 1819 to struggling rural parents, he was on his own at the age of 12, learning the trade of a printer. For much of his young manhood he alternated between working as a printer, country schoolteacher, and journalist. In this last capacity he held a score of short-lived posts, editing and writing for papers in Manhattan and Brooklyn. dur ing the Civil War he nursed wounded soldiers in Washington, where he remained for several years afterward as a government clerk.

But his real work, his life's work, was "Leaves of Grass," which he continually expanded, revised, and rewrote practically until the day of his death in 1892. The loosely structured rhythms of his unmeasured poetry, together with the grandness of its scope, captivated the likes of Emerson, Bronson Alcott, and Henry David Thoreau. They were less comfortable with its undisguised sensuality; Thoreau declared that parts of the book "were as though the beasts spoke." Whitman's encounters with the Concord transcendentalists form one of the biography's most insightful -- and amusing -- aspects. When Thoreau paid a visit to Whitman, the two legendary nonconformists were so on edge that Bronson Alcott described them as "two beasts, each wondering what the other would do, snap or run."

When Emerson read the first edition of "Leaves of Grass" in 1855 he was prompted to send Whitman a congratulatory letter stating, "I greet you at the beginning of a great career." Yet toward the end of that career Whitman felt Emerson grow considerably cooler; in his 1874 anthology of American poetry, "Parnassus," Emerson included not a line of Whitman's work.

Ironically, most of the American poet's acclaim during his lifetime came not from his countrymen but from the English. In his own country he was something of a curiosity, known for his flowing white beard, wide felt hat, and rumpled clothes. For all that he used his unconventional image promote his work --box label, although he did not smoke. "Leaves of Grass" yielded him no monetary profit; in fact most of the editions were printed by Whitman himself. For most of his life the unmarried, homosexual poet lived with relatives; at the age of 65, a semi-invalid, he managed to buy a modest house in Camden, N.J.

Despite a lengthy probe of some of the baser aspects of Whitman's life, this sensitive biography captures the exuberant spirit and extraordinary originality of its subject. No easy task when dealing with a poet who, in "Song of Myself," declared himself to be a "kosmos" and then proceeded to identify himself with all of nature and humanity.