The general consensus on Whitman is that he first appeared in Canonical literature as a voice for the workingman. The era in which Leaves of Grass first appeared (1855-1860) were crucial years in the Industrial Revolution in England. To be brief on the importance of this era, it signaled an explosion of productivity and the appearance of material wealth the likes of which the world had never seen before. The creation of this plenty was enabled through the use of machines, which was completely revolutionary when compared to previous human history. Wealth began to be measured in terms of mechanical output that was merely powered by human hands. From this, the notions of capitalism rose, and with them, the a new conception of the master / slave relationship. This is not to say that slaves and masters had not existed before, but with the creation of these new machines the potential for a greater separation between the slave (laborer) and the master(factory owner) became more apparent and widespread. This was not lost upon the great minds of the era, including Frederick Engels, Karl Marx, and of course, Walt Whitman. Poor working Conditions of the laboring class were shared on both sides of the Atlantic. While the industrial revolution of course hit England much sooner than the United States, the line between upper/master and lower/laborer classes became much more defined in both instances.
This having been said, it raised the question of what the ideal human existence might be. The appearance of increased productivity shifted the critical minds of authors towards the innate human qualities that we as a race retained despite the sudden appearance of railroads or instant communication by means the telegraph that precipitated the widening of material wealth amongst populations. As a noted influence on the famous Karl Marx, Frederick Engels wrote of the pre-industrial Britain: “So the workers vegetated throughout a passably comfortable existence, leading a righteous and peaceful life in all piety and probity…their children grew up in the fresh country air.” Now I encourage you to take in Marx’s view of the industrialized world: “The discovery of gold and silver in America, the extirpation, enslavement, and entombment in the mines of the aboriginal population, the beginning of the conquest and looting of the East Indies, the turning of Africa into a warren for the commercial hunting of blackskins, signalized the rosy dawn of the era of capitalist production.”
In response to this difficult question, Whitman produces his response in “A Song for Occupations”: “Because you are greasy or pimpled, or that you were once drunk, or a thief, or diseased, or rheumatic, or a prostitute, or are so now; or from frivolity or impotence, or that you are no scholar, and never saw your name in print, Do you give in that you are any less immortal?” I find that the most important word in this passage is its final one; “Immortal.” Clearly Whitman feels that the position one holds in terms of material possession matters not when posed with the question of what it means to be human. He feels that the idea of being a human and possessing independent thought gives a worth to an individual that no amount of physical possession could match.