Joaquin Miller is the pseudonym of Cincinnatus Hiner. He was a minor but colorful poet whose romantic verse, plays, and prose mainly glorified the West. His most important works are Songs of the Sierras (1871) and Life Amongst the Modocs (1873).
Although Miller and Whitman were personally acquainted, read each other's works, and briefly corresponded, they were both on the peripheries of the other's circle. There appears to be no influence of Miller on Whitman and only superficial influence in the other direction. Miller wrote "To Walt Whitman" (1877) and included him in the elegy "The Passing of Tennyson" (1896) as one in a procession of recently deceased great poets.
The bulk of Miller's poetry was written in tetrameter, an indication of how little impact Whitman's style had on him. The sweep and grandeur of Whitman's subject matter, his romantic idealism, and his personal example of standing out as an individual were likely the qualities which appealed to Miller. The mild interest that the two poets had in each other derived more from their professional relationship than from a sharing of principles.
Bibliography
Brooks, Van Wyck. The Times of Melville and Whitman. New York: Dutton, 1947.
Frost, O.W. Joaquin Miller. New York: Twayne, 1967.
Miller, Joaquin. The Poetical Works of Joaquin Miller. Ed. Stuart P. Sherman. New York: Putnam, 1923.