Walt Whitman, was one of America’s greatest poets and famous for his collection Leaves of Grass, a collection widely regarded as the finest in American literature.
Whitman was born in 1819, in West Hills, Long Island, and grew up in Brooklyn, New York. His father was a Quaker carpenter, while his mother took care of he and his eight siblings. He attended rural schools and trained as a printer, but his deep love of reading saw him yearn for a career as a journalist. He started a weekly paper called the LongIslander and also taught school for a while.
Eventually he was drawn to newspapers in New York City and began working as a journalist. Back in New York, Whitman witnessed the rapid influx of immigrants coming to the United States to find freedom and open spaces. These images greatly influenced the young journalist and would inform the ideas in his developing poetry.
During this time his poetry was generally regarded as dire and met with little interest.
In 1848 he was fired from his job at the Brooklyn Eagle over political differences with his editor and he traveled to New Orleans to work on a paper in that city. He was awed by the size and beauty of the country.
After his return to New York City a few months later, Whitman went through a transformation. The hack poetry was replaced by something more profound. He began writing the poems that would make up the first version of Leaves of Grass. 
At the age of 36, Whitman paid for the publication of the first edition of Leaves of Grass himself as no publisher would accept them. The First Edition published in 1855, sold poorly and received little critical notice. Its use of colloquial American speech, its slang, its free verse style with its rejection of rhyme and meter and its subject matter weighted in the world of industry and the common man was not met with much enthusiasm. However, Whitman sent America’s foremost poet of the day, Ralph Waldo Emerson, a copy Emerson’s famous reply “I find it the most extraordinary piece of wit and wisdom that America has yet contributed...I greet you at the beginning of a great career,” encouraged Whitman to continue.

For the rest of his life Whitman would continue to revise and update, expand and edit the collection going from 12 poems in the first edition to more than 100 in later editions. Over a 37-year period, Whitman published nine separate editions of his masterpiece. The final, 1892 edition, is the one most familiar to readers today. His work had a profound  influence on the direction of 20th-century American poets, especially Ezra Pound, William Carlos Williams, Carl Sandburg, Allen Ginsberg and other “beat” poets.
In the mid 1860s Whitman served as a nurse at a Virginia army hospital during the American Civil War. After the war he published Drum-Taps, a collection of poems relating his experience of war, which included perhaps his single most famous poem ‘O Captain! My Captain!’ about the assassination of President Abraham Lincoln.

In January 1865 Whitman took a clerk’s position in the Indian Bureau of the Department of the Interior. He kept a blue covered working copy of his revisions for Leaves of Grass, the so-called Blue Book, in his desk at the Bureau. The secretary of the interior discovered the copy and was so scandalized by its sexual references that he dismissed Whitman from his job in June 1865. A result of this was the publication of “The Good Gray Poet: A Vindication, written by Whitman’s good friend William Douglas O’Connor in which O’Connor lauded Whitman’s genius and the injustice of his firing. This book began the movement to lionize Whitman as a great poet, a movement that is still strong today.  Whitman regained a position in the government this time in the Attorney General’s Office.
Later that year, Whitman published Sequel to Drum-Taps, whose best-known poem was the great elegy on Abraham Lincoln, “When Lilacs Last in the Dooryard Bloom’d.”
Whitman was also receiving critical acclaim abroad, especially in England. His poetry too began to take on a more universal nature and became preoccupied with notions of death and the soul. 
Over the next decade Whitman’s output remained constant. He continued to revise and publish new editions of Leaves of Grass and poems, such as “Whispers of Heavenly Death,” “Darest Thou Now O Soul,” “The Last Invocation,” and “A Noiseless Patient Spider,” and “Passage to India,” which are regarded as some of his most important.
Despite his growing despondency about the growth of corruption in the US and the poor results of the so called reconstruction following the civil war, in 1871 Whitman published Democratic Vista’s, perhaps his most important work of prose to much acclaim. 
In 1873 Whitman suffered a stroke and moved from Washington to Camden, N.J. There he spent the rest of his life revising Leaves and occasionally traveling. In 1881 Whitman settled on the final arrangement of the poems in Leaves of Grass, and thereafter no revisions were made. He died in 1892