Thanks for calling out the Whitman Archive! I worked to digitize the manuscript & early first editions of Leaves of Grass while an undergraduate at UVA, and both had a great time and learned a ton about Whitman and old books.
To make a modern comparison, scholars believe Whitman authored Leaves of Grass in a very similar way to how Kanye West is treating The Life of Pablo. He released a rough draft to a limited audience over a short period of time, but continued editing, revising and adding to it for years afterward, as his perspective and understanding of the world around him evolved.
Whitman was an amazing writer. I wouldn't hesitate to call him America's Joyce.
rather than this being because of his work directly, it's more because he understood and lived the idea that change is inevitable and necessary
he only wrote one book his entire life
publishing edits through the years
it is amazing to see how the poems both change and remain the same over time
when i read a whitman piece i always read it as i know he himself would have:
http://whitmanarchive.org/