With the publication of "Trees" in the magazine "Poetry" in August 1913, Kilmer gained immense popularity as a poet across the United States. He had established himself as a successful lecturer—particularly one seeking to reach a Catholic audience. His close friend and editor Robert Holliday wrote that it "is not an unsupported assertion to say that he was in his time and place the laureate of the Catholic Church." "Trees and Other Poems" (1914) was published the following year. This collection also introduced the popular poem "The House With Nobody In It". Over the next few years, Kilmer was prolific in his output, managing an intense schedule of lectures, publishing a large number of essays and literary criticism, and writing poetry. In 1915 he became poetry editor of "Current Literature" and contributing editor of "Warner's Library of the World's Best Literature". In 1916 and 1917, before the American entry into World War I, Kilmer would publish four books: "The Circus and Other Essays" (1916), a series of interviews with literary personages entitled "Literature in the Making" (1917), "Main Street and Other Poems" (1917), and "Dreams and Images: An Anthology of Catholic Poets" (1917).