Whitman's collection of poems in Leaves of Grass is usually interpreted according to the individual poems contained within its individual editions. The editions were of varying length, each one larger and augmented from the previous version, until the final edition reached over 400 poems. Discussion is often focused also upon the major editions of Leaves of Grass often associated with the very early respective versions of 1855 and 1856, to the 1860 edition, and finally to editions very late in Whitman's life which also included the significant Whitman poem When Lilacs Last in the Dooryard Bloom'd. The 1855 edition is particularly notable for the inclusion of the two poems Song of Myself and The Sleepers. The 1856 edition included the notable Whitman poem Crossing Brooklyn Ferry. In the 1860 edition, Whitman further added the major poems A Word Out of the Sea and As I Ebb'd With the Ocean of Life. The specific interpretation of many of Whitman's major poems may be found in the articles associated with those individual poems.
Particularly in Song of Myself, Whitman emphasized an all-powerful "I" who serves as narrator. The "I" tries to relieve both social and private problems by using powerful affirmative cultural images. The emphasis on American culture helped reach Whitman's intention of creating a distinctly American epic poem comparable to the works of Homer. Originally written at a time of significant urbanization in America, Leaves of Grass responds to the impact urbanization has on the masses. However, the title metaphor of grass indicates a pastoral vision of rural idealism. The poem When Lilacs Last in the Dooryard Bloom'd is Whitman's elegy to Lincoln after his death.