The Vault at Pfaff'sMention
"It may have been at Pfaff's that Whitman met Fred Vaughan, an intriguing mystery-figure in Whitman biography. Whitman and Vaughan, a young Irish stage driver, clearly had an intense relationship at this time, perhaps inspiring the sequence of homoerotic love poems Whitman called 'Live Oak, with Moss,' poems that would become the heart of his Calamus cluster, which appeared in the 1860 edition of Leaves. These poems record a despair about the failure of the relationship, and the loss of Whitman's bond with Vaughan--who soon married, had four children, and would only sporadically keep in touch with Whitman--was clearly the source of some deep unhappiness for the poet."
Circa